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+/* SPDX-License-Identifier: GPL-2.0
+ *
+ * IO cost model based controller.
+ *
+ * Copyright (C) 2019 Tejun Heo <tj@kernel.org>
+ * Copyright (C) 2019 Andy Newell <newella@fb.com>
+ * Copyright (C) 2019 Facebook
+ *
+ * One challenge of controlling IO resources is the lack of trivially
+ * observable cost metric. This is distinguished from CPU and memory where
+ * wallclock time and the number of bytes can serve as accurate enough
+ * approximations.
+ *
+ * Bandwidth and iops are the most commonly used metrics for IO devices but
+ * depending on the type and specifics of the device, different IO patterns
+ * easily lead to multiple orders of magnitude variations rendering them
+ * useless for the purpose of IO capacity distribution. While on-device
+ * time, with a lot of clutches, could serve as a useful approximation for
+ * non-queued rotational devices, this is no longer viable with modern
+ * devices, even the rotational ones.
+ *
+ * While there is no cost metric we can trivially observe, it isn't a
+ * complete mystery. For example, on a rotational device, seek cost
+ * dominates while a contiguous transfer contributes a smaller amount
+ * proportional to the size. If we can characterize at least the relative
+ * costs of these different types of IOs, it should be possible to
+ * implement a reasonable work-conserving proportional IO resource
+ * distribution.
+ *
+ * 1. IO Cost Model
+ *
+ * IO cost model estimates the cost of an IO given its basic parameters and
+ * history (e.g. the end sector of the last IO). The cost is measured in
+ * device time. If a given IO is estimated to cost 10ms, the device should
+ * be able to process ~100 of those IOs in a second.
+ *
+ * Currently, there's only one builtin cost model - linear. Each IO is
+ * classified as sequential or random and given a base cost accordingly.
+ * On top of that, a size cost proportional to the length of the IO is
+ * added. While simple, this model captures the operational
+ * characteristics of a wide varienty of devices well enough. Default
+ * paramters for several different classes of devices are provided and the
+ * parameters can be configured from userspace via
+ * /sys/fs/cgroup/io.cost.model.
+ *
+ * If needed, tools/cgroup/iocost_coef_gen.py can be used to generate
+ * device-specific coefficients.
+ *
+ * 2. Control Strategy
+ *
+ * The device virtual time (vtime) is used as the primary control metric.
+ * The control strategy is composed of the following three parts.
+ *
+ * 2-1. Vtime Distribution
+ *
+ * When a cgroup becomes active in terms of IOs, its hierarchical share is
+ * calculated. Please consider the following hierarchy where the numbers
+ * inside parentheses denote the configured weights.
+ *
+ * root
+ * / \
+ * A (w:100) B (w:300)
+ * / \
+ * A0 (w:100) A1 (w:100)
+ *
+ * If B is idle and only A0 and A1 are actively issuing IOs, as the two are
+ * of equal weight, each gets 50% share. If then B starts issuing IOs, B
+ * gets 300/(100+300) or 75% share, and A0 and A1 equally splits the rest,
+ * 12.5% each. The distribution mechanism only cares about these flattened
+ * shares. They're called hweights (hierarchical weights) and always add
+ * upto 1 (WEIGHT_ONE).
+ *
+ * A given cgroup's vtime runs slower in inverse proportion to its hweight.
+ * For example, with 12.5% weight, A0's time runs 8 times slower (100/12.5)
+ * against the device vtime - an IO which takes 10ms on the underlying
+ * device is considered to take 80ms on A0.
+ *
+ * This constitutes the basis of IO capacity distribution. Each cgroup's
+ * vtime is running at a rate determined by its hweight. A cgroup tracks
+ * the vtime consumed by past IOs and can issue a new IO iff doing so
+ * wouldn't outrun the current device vtime. Otherwise, the IO is
+ * suspended until the vtime has progressed enough to cover it.
+ *
+ * 2-2. Vrate Adjustment
+ *
+ * It's unrealistic to expect the cost model to be perfect. There are too
+ * many devices and even on the same device the overall performance
+ * fluctuates depending on numerous factors such as IO mixture and device
+ * internal garbage collection. The controller needs to adapt dynamically.
+ *
+ * This is achieved by adjusting the overall IO rate according to how busy
+ * the device is. If the device becomes overloaded, we're sending down too
+ * many IOs and should generally slow down. If there are waiting issuers
+ * but the device isn't saturated, we're issuing too few and should
+ * generally speed up.
+ *
+ * To slow down, we lower the vrate - the rate at which the device vtime
+ * passes compared to the wall clock. For example, if the vtime is running
+ * at the vrate of 75%, all cgroups added up would only be able to issue
+ * 750ms worth of IOs per second, and vice-versa for speeding up.
+ *
+ * Device business is determined using two criteria - rq wait and
+ * completion latencies.
+ *
+ * When a device gets saturated, the on-device and then the request queues
+ * fill up and a bio which is ready to be issued has to wait for a request
+ * to become available. When this delay becomes noticeable, it's a clear
+ * indication that the device is saturated and we lower the vrate. This
+ * saturation signal is fairly conservative as it only triggers when both
+ * hardware and software queues are filled up, and is used as the default
+ * busy signal.
+ *
+ * As devices can have deep queues and be unfair in how the queued commands
+ * are executed, soley depending on rq wait may not result in satisfactory
+ * control quality. For a better control quality, completion latency QoS
+ * parameters can be configured so that the device is considered saturated
+ * if N'th percentile completion latency rises above the set point.
+ *
+ * The completion latency requirements are a function of both the
+ * underlying device characteristics and the desired IO latency quality of
+ * service. There is an inherent trade-off - the tighter the latency QoS,
+ * the higher the bandwidth lossage. Latency QoS is disabled by default
+ * and can be set through /sys/fs/cgroup/io.cost.qos.
+ *
+ * 2-3. Work Conservation
+ *
+ * Imagine two cgroups A and B with equal weights. A is issuing a small IO
+ * periodically while B is sending out enough parallel IOs to saturate the
+ * device on its own. Let's say A's usage amounts to 100ms worth of IO
+ * cost per second, i.e., 10% of the device capacity. The naive
+ * distribution of half and half would lead to 60% utilization of the
+ * device, a significant reduction in the total amount of work done
+ * compared to free-for-all competition. This is too high a cost to pay
+ * for IO control.
+ *
+ * To conserve the total amount of work done, we keep track of how much
+ * each active cgroup is actually using and yield part of its weight if
+ * there are other cgroups which can make use of it. In the above case,
+ * A's weight will be lowered so that it hovers above the actual usage and
+ * B would be able to use the rest.
+ *
+ * As we don't want to penalize a cgroup for donating its weight, the
+ * surplus weight adjustment factors in a margin and has an immediate
+ * snapback mechanism in case the cgroup needs more IO vtime for itself.
+ *
+ * Note that adjusting down surplus weights has the same effects as
+ * accelerating vtime for other cgroups and work conservation can also be
+ * implemented by adjusting vrate dynamically. However, squaring who can
+ * donate and should take back how much requires hweight propagations
+ * anyway making it easier to implement and understand as a separate
+ * mechanism.
+ *
+ * 3. Monitoring
+ *
+ * Instead of debugfs or other clumsy monitoring mechanisms, this
+ * controller uses a drgn based monitoring script -
+ * tools/cgroup/iocost_monitor.py. For details on drgn, please see
+ * https://github.com/osandov/drgn. The ouput looks like the following.
+ *
+ * sdb RUN per=300ms cur_per=234.218:v203.695 busy= +1 vrate= 62.12%
+ * active weight hweight% inflt% dbt delay usages%
+ * test/a * 50/ 50 33.33/ 33.33 27.65 2 0*041 033:033:033
+ * test/b * 100/ 100 66.67/ 66.67 17.56 0 0*000 066:079:077
+ *
+ * - per : Timer period
+ * - cur_per : Internal wall and device vtime clock
+ * - vrate : Device virtual time rate against wall clock
+ * - weight : Surplus-adjusted and configured weights
+ * - hweight : Surplus-adjusted and configured hierarchical weights
+ * - inflt : The percentage of in-flight IO cost at the end of last period
+ * - del_ms : Deferred issuer delay induction level and duration
+ * - usages : Usage history
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/timer.h>
+#include <linux/time64.h>
+#include <linux/parser.h>
+#include <linux/sched/signal.h>
+#include <linux/blk-cgroup.h>
+#include <asm/local.h>
+#include <asm/local64.h>
+#include "blk-rq-qos.h"
+#include "blk-stat.h"
+#include "blk-wbt.h"
+
+#ifdef CONFIG_TRACEPOINTS
+
+/* copied from TRACE_CGROUP_PATH, see cgroup-internal.h */
+#define TRACE_IOCG_PATH_LEN 1024
+static DEFINE_SPINLOCK(trace_iocg_path_lock);
+static char trace_iocg_path[TRACE_IOCG_PATH_LEN];
+
+#define TRACE_IOCG_PATH(type, iocg, ...) \
+ do { \
+ unsigned long flags; \
+ if (trace_iocost_##type##_enabled()) { \
+ spin_lock_irqsave(&trace_iocg_path_lock, flags); \
+ cgroup_path(iocg_to_blkg(iocg)->blkcg->css.cgroup, \
+ trace_iocg_path, TRACE_IOCG_PATH_LEN); \
+ trace_iocost_##type(iocg, trace_iocg_path, \
+ ##__VA_ARGS__); \
+ spin_unlock_irqrestore(&trace_iocg_path_lock, flags); \
+ } \
+ } while (0)
+
+#else /* CONFIG_TRACE_POINTS */
+#define TRACE_IOCG_PATH(type, iocg, ...) do { } while (0)
+#endif /* CONFIG_TRACE_POINTS */
+
+enum {
+ MILLION = 1000000,
+
+ /* timer period is calculated from latency requirements, bound it */
+ MIN_PERIOD = USEC_PER_MSEC,
+ MAX_PERIOD = USEC_PER_SEC,
+
+ /*
+ * iocg->vtime is targeted at 50% behind the device vtime, which
+ * serves as its IO credit buffer. Surplus weight adjustment is
+ * immediately canceled if the vtime margin runs below 10%.
+ */
+ MARGIN_MIN_PCT = 10,
+ MARGIN_LOW_PCT = 20,
+ MARGIN_TARGET_PCT = 50,
+
+ INUSE_ADJ_STEP_PCT = 25,
+
+ /* Have some play in timer operations */
+ TIMER_SLACK_PCT = 1,
+
+ /* 1/64k is granular enough and can easily be handled w/ u32 */
+ WEIGHT_ONE = 1 << 16,
+};
+
+enum {
+ /*
+ * As vtime is used to calculate the cost of each IO, it needs to
+ * be fairly high precision. For example, it should be able to
+ * represent the cost of a single page worth of discard with
+ * suffificient accuracy. At the same time, it should be able to
+ * represent reasonably long enough durations to be useful and
+ * convenient during operation.
+ *
+ * 1s worth of vtime is 2^37. This gives us both sub-nanosecond
+ * granularity and days of wrap-around time even at extreme vrates.
+ */
+ VTIME_PER_SEC_SHIFT = 37,
+ VTIME_PER_SEC = 1LLU << VTIME_PER_SEC_SHIFT,
+ VTIME_PER_USEC = VTIME_PER_SEC / USEC_PER_SEC,
+ VTIME_PER_NSEC = VTIME_PER_SEC / NSEC_PER_SEC,
+
+ /* bound vrate adjustments within two orders of magnitude */
+ VRATE_MIN_PPM = 10000, /* 1% */
+ VRATE_MAX_PPM = 100000000, /* 10000% */
+
+ VRATE_MIN = VTIME_PER_USEC * VRATE_MIN_PPM / MILLION,
+ VRATE_CLAMP_ADJ_PCT = 4,
+
+ /* switch iff the conditions are met for longer than this */
+ AUTOP_CYCLE_NSEC = 10LLU * NSEC_PER_SEC,
+};
+
+enum {
+ /* if IOs end up waiting for requests, issue less */
+ RQ_WAIT_BUSY_PCT = 5,
+
+ /* unbusy hysterisis */
+ UNBUSY_THR_PCT = 75,
+
+ /*
+ * The effect of delay is indirect and non-linear and a huge amount of
+ * future debt can accumulate abruptly while unthrottled. Linearly scale
+ * up delay as debt is going up and then let it decay exponentially.
+ * This gives us quick ramp ups while delay is accumulating and long
+ * tails which can help reducing the frequency of debt explosions on
+ * unthrottle. The parameters are experimentally determined.
+ *
+ * The delay mechanism provides adequate protection and behavior in many
+ * cases. However, this is far from ideal and falls shorts on both
+ * fronts. The debtors are often throttled too harshly costing a
+ * significant level of fairness and possibly total work while the
+ * protection against their impacts on the system can be choppy and
+ * unreliable.
+ *
+ * The shortcoming primarily stems from the fact that, unlike for page
+ * cache, the kernel doesn't have well-defined back-pressure propagation
+ * mechanism and policies for anonymous memory. Fully addressing this
+ * issue will likely require substantial improvements in the area.
+ */
+ MIN_DELAY_THR_PCT = 500,
+ MAX_DELAY_THR_PCT = 25000,
+ MIN_DELAY = 250,
+ MAX_DELAY = 250 * USEC_PER_MSEC,
+
+ /* halve debts if avg usage over 100ms is under 50% */
+ DFGV_USAGE_PCT = 50,
+ DFGV_PERIOD = 100 * USEC_PER_MSEC,
+
+ /* don't let cmds which take a very long time pin lagging for too long */
+ MAX_LAGGING_PERIODS = 10,
+
+ /*
+ * Count IO size in 4k pages. The 12bit shift helps keeping
+ * size-proportional components of cost calculation in closer
+ * numbers of digits to per-IO cost components.
+ */
+ IOC_PAGE_SHIFT = 12,
+ IOC_PAGE_SIZE = 1 << IOC_PAGE_SHIFT,
+ IOC_SECT_TO_PAGE_SHIFT = IOC_PAGE_SHIFT - SECTOR_SHIFT,
+
+ /* if apart further than 16M, consider randio for linear model */
+ LCOEF_RANDIO_PAGES = 4096,
+};
+
+enum ioc_running {
+ IOC_IDLE,
+ IOC_RUNNING,
+ IOC_STOP,
+};
+
+/* io.cost.qos controls including per-dev enable of the whole controller */
+enum {
+ QOS_ENABLE,
+ QOS_CTRL,
+ NR_QOS_CTRL_PARAMS,
+};
+
+/* io.cost.qos params */
+enum {
+ QOS_RPPM,
+ QOS_RLAT,
+ QOS_WPPM,
+ QOS_WLAT,
+ QOS_MIN,
+ QOS_MAX,
+ NR_QOS_PARAMS,
+};
+
+/* io.cost.model controls */
+enum {
+ COST_CTRL,
+ COST_MODEL,
+ NR_COST_CTRL_PARAMS,
+};
+
+/* builtin linear cost model coefficients */
+enum {
+ I_LCOEF_RBPS,
+ I_LCOEF_RSEQIOPS,
+ I_LCOEF_RRANDIOPS,
+ I_LCOEF_WBPS,
+ I_LCOEF_WSEQIOPS,
+ I_LCOEF_WRANDIOPS,
+ NR_I_LCOEFS,
+};
+
+enum {
+ LCOEF_RPAGE,
+ LCOEF_RSEQIO,
+ LCOEF_RRANDIO,
+ LCOEF_WPAGE,
+ LCOEF_WSEQIO,
+ LCOEF_WRANDIO,
+ NR_LCOEFS,
+};
+
+enum {
+ AUTOP_INVALID,
+ AUTOP_HDD,
+ AUTOP_SSD_QD1,
+ AUTOP_SSD_DFL,
+ AUTOP_SSD_FAST,
+};
+
+struct ioc_gq;
+
+struct ioc_params {
+ u32 qos[NR_QOS_PARAMS];
+ u64 i_lcoefs[NR_I_LCOEFS];
+ u64 lcoefs[NR_LCOEFS];
+ u32 too_fast_vrate_pct;
+ u32 too_slow_vrate_pct;
+};
+
+struct ioc_margins {
+ s64 min;
+ s64 low;
+ s64 target;
+};
+
+struct ioc_missed {
+ local_t nr_met;
+ local_t nr_missed;
+ u32 last_met;
+ u32 last_missed;
+};
+
+struct ioc_pcpu_stat {
+ struct ioc_missed missed[2];
+
+ local64_t rq_wait_ns;
+ u64 last_rq_wait_ns;
+};
+
+/* per device */
+struct ioc {
+ struct rq_qos rqos;
+
+ bool enabled;
+
+ struct ioc_params params;
+ struct ioc_margins margins;
+ u32 period_us;
+ u32 timer_slack_ns;
+ u64 vrate_min;
+ u64 vrate_max;
+
+ spinlock_t lock;
+ struct timer_list timer;
+ struct list_head active_iocgs; /* active cgroups */
+ struct ioc_pcpu_stat __percpu *pcpu_stat;
+
+ enum ioc_running running;
+ atomic64_t vtime_rate;
+ u64 vtime_base_rate;
+ s64 vtime_err;
+
+ seqcount_spinlock_t period_seqcount;
+ u64 period_at; /* wallclock starttime */
+ u64 period_at_vtime; /* vtime starttime */
+
+ atomic64_t cur_period; /* inc'd each period */
+ int busy_level; /* saturation history */
+
+ bool weights_updated;
+ atomic_t hweight_gen; /* for lazy hweights */
+
+ /* debt forgivness */
+ u64 dfgv_period_at;
+ u64 dfgv_period_rem;
+ u64 dfgv_usage_us_sum;
+
+ u64 autop_too_fast_at;
+ u64 autop_too_slow_at;
+ int autop_idx;
+ bool user_qos_params:1;
+ bool user_cost_model:1;
+};
+
+struct iocg_pcpu_stat {
+ local64_t abs_vusage;
+};
+
+struct iocg_stat {
+ u64 usage_us;
+ u64 wait_us;
+ u64 indebt_us;
+ u64 indelay_us;
+};
+
+/* per device-cgroup pair */
+struct ioc_gq {
+ struct blkg_policy_data pd;
+ struct ioc *ioc;
+
+ /*
+ * A iocg can get its weight from two sources - an explicit
+ * per-device-cgroup configuration or the default weight of the
+ * cgroup. `cfg_weight` is the explicit per-device-cgroup
+ * configuration. `weight` is the effective considering both
+ * sources.
+ *
+ * When an idle cgroup becomes active its `active` goes from 0 to
+ * `weight`. `inuse` is the surplus adjusted active weight.
+ * `active` and `inuse` are used to calculate `hweight_active` and
+ * `hweight_inuse`.
+ *
+ * `last_inuse` remembers `inuse` while an iocg is idle to persist
+ * surplus adjustments.
+ *
+ * `inuse` may be adjusted dynamically during period. `saved_*` are used
+ * to determine and track adjustments.
+ */
+ u32 cfg_weight;
+ u32 weight;
+ u32 active;
+ u32 inuse;
+
+ u32 last_inuse;
+ s64 saved_margin;
+
+ sector_t cursor; /* to detect randio */
+
+ /*
+ * `vtime` is this iocg's vtime cursor which progresses as IOs are
+ * issued. If lagging behind device vtime, the delta represents
+ * the currently available IO budget. If runnning ahead, the
+ * overage.
+ *
+ * `vtime_done` is the same but progressed on completion rather
+ * than issue. The delta behind `vtime` represents the cost of
+ * currently in-flight IOs.
+ */
+ atomic64_t vtime;
+ atomic64_t done_vtime;
+ u64 abs_vdebt;
+
+ /* current delay in effect and when it started */
+ u64 delay;
+ u64 delay_at;
+
+ /*
+ * The period this iocg was last active in. Used for deactivation
+ * and invalidating `vtime`.
+ */
+ atomic64_t active_period;
+ struct list_head active_list;
+
+ /* see __propagate_weights() and current_hweight() for details */
+ u64 child_active_sum;
+ u64 child_inuse_sum;
+ u64 child_adjusted_sum;
+ int hweight_gen;
+ u32 hweight_active;
+ u32 hweight_inuse;
+ u32 hweight_donating;
+ u32 hweight_after_donation;
+
+ struct list_head walk_list;
+ struct list_head surplus_list;
+
+ struct wait_queue_head waitq;
+ struct hrtimer waitq_timer;
+
+ /* timestamp at the latest activation */
+ u64 activated_at;
+
+ /* statistics */
+ struct iocg_pcpu_stat __percpu *pcpu_stat;
+ struct iocg_stat local_stat;
+ struct iocg_stat desc_stat;
+ struct iocg_stat last_stat;
+ u64 last_stat_abs_vusage;
+ u64 usage_delta_us;
+ u64 wait_since;
+ u64 indebt_since;
+ u64 indelay_since;
+
+ /* this iocg's depth in the hierarchy and ancestors including self */
+ int level;
+ struct ioc_gq *ancestors[];
+};
+
+/* per cgroup */
+struct ioc_cgrp {
+ struct blkcg_policy_data cpd;
+ unsigned int dfl_weight;
+};
+
+struct ioc_now {
+ u64 now_ns;
+ u64 now;
+ u64 vnow;
+ u64 vrate;
+};
+
+struct iocg_wait {
+ struct wait_queue_entry wait;
+ struct bio *bio;
+ u64 abs_cost;
+ bool committed;
+};
+
+struct iocg_wake_ctx {
+ struct ioc_gq *iocg;
+ u32 hw_inuse;
+ s64 vbudget;
+};
+
+static const struct ioc_params autop[] = {
+ [AUTOP_HDD] = {
+ .qos = {
+ [QOS_RLAT] = 250000, /* 250ms */
+ [QOS_WLAT] = 250000,
+ [QOS_MIN] = VRATE_MIN_PPM,
+ [QOS_MAX] = VRATE_MAX_PPM,
+ },
+ .i_lcoefs = {
+ [I_LCOEF_RBPS] = 174019176,
+ [I_LCOEF_RSEQIOPS] = 41708,
+ [I_LCOEF_RRANDIOPS] = 370,
+ [I_LCOEF_WBPS] = 178075866,
+ [I_LCOEF_WSEQIOPS] = 42705,
+ [I_LCOEF_WRANDIOPS] = 378,
+ },
+ },
+ [AUTOP_SSD_QD1] = {
+ .qos = {
+ [QOS_RLAT] = 25000, /* 25ms */
+ [QOS_WLAT] = 25000,
+ [QOS_MIN] = VRATE_MIN_PPM,
+ [QOS_MAX] = VRATE_MAX_PPM,
+ },
+ .i_lcoefs = {
+ [I_LCOEF_RBPS] = 245855193,
+ [I_LCOEF_RSEQIOPS] = 61575,
+ [I_LCOEF_RRANDIOPS] = 6946,
+ [I_LCOEF_WBPS] = 141365009,
+ [I_LCOEF_WSEQIOPS] = 33716,
+ [I_LCOEF_WRANDIOPS] = 26796,
+ },
+ },
+ [AUTOP_SSD_DFL] = {
+ .qos = {
+ [QOS_RLAT] = 25000, /* 25ms */
+ [QOS_WLAT] = 25000,
+ [QOS_MIN] = VRATE_MIN_PPM,
+ [QOS_MAX] = VRATE_MAX_PPM,
+ },
+ .i_lcoefs = {
+ [I_LCOEF_RBPS] = 488636629,
+ [I_LCOEF_RSEQIOPS] = 8932,
+ [I_LCOEF_RRANDIOPS] = 8518,
+ [I_LCOEF_WBPS] = 427891549,
+ [I_LCOEF_WSEQIOPS] = 28755,
+ [I_LCOEF_WRANDIOPS] = 21940,
+ },
+ .too_fast_vrate_pct = 500,
+ },
+ [AUTOP_SSD_FAST] = {
+ .qos = {
+ [QOS_RLAT] = 5000, /* 5ms */
+ [QOS_WLAT] = 5000,
+ [QOS_MIN] = VRATE_MIN_PPM,
+ [QOS_MAX] = VRATE_MAX_PPM,
+ },
+ .i_lcoefs = {
+ [I_LCOEF_RBPS] = 3102524156LLU,
+ [I_LCOEF_RSEQIOPS] = 724816,
+ [I_LCOEF_RRANDIOPS] = 778122,
+ [I_LCOEF_WBPS] = 1742780862LLU,
+ [I_LCOEF_WSEQIOPS] = 425702,
+ [I_LCOEF_WRANDIOPS] = 443193,
+ },
+ .too_slow_vrate_pct = 10,
+ },
+};
+
+/*
+ * vrate adjust percentages indexed by ioc->busy_level. We adjust up on
+ * vtime credit shortage and down on device saturation.
+ */
+static u32 vrate_adj_pct[] =
+ { 0, 0, 0, 0,
+ 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+ 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
+ 4, 4, 4, 4, 4, 4, 4, 4, 8, 8, 8, 8, 8, 8, 8, 8, 16 };
+
+static struct blkcg_policy blkcg_policy_iocost;
+
+/* accessors and helpers */
+static struct ioc *rqos_to_ioc(struct rq_qos *rqos)
+{
+ return container_of(rqos, struct ioc, rqos);
+}
+
+static struct ioc *q_to_ioc(struct request_queue *q)
+{
+ return rqos_to_ioc(rq_qos_id(q, RQ_QOS_COST));
+}
+
+static const char *q_name(struct request_queue *q)
+{
+ if (blk_queue_registered(q))
+ return kobject_name(q->kobj.parent);
+ else
+ return "<unknown>";
+}
+
+static const char __maybe_unused *ioc_name(struct ioc *ioc)
+{
+ return q_name(ioc->rqos.q);
+}
+
+static struct ioc_gq *pd_to_iocg(struct blkg_policy_data *pd)
+{
+ return pd ? container_of(pd, struct ioc_gq, pd) : NULL;
+}
+
+static struct ioc_gq *blkg_to_iocg(struct blkcg_gq *blkg)
+{
+ return pd_to_iocg(blkg_to_pd(blkg, &blkcg_policy_iocost));
+}
+
+static struct blkcg_gq *iocg_to_blkg(struct ioc_gq *iocg)
+{
+ return pd_to_blkg(&iocg->pd);
+}
+
+static struct ioc_cgrp *blkcg_to_iocc(struct blkcg *blkcg)
+{
+ return container_of(blkcg_to_cpd(blkcg, &blkcg_policy_iocost),
+ struct ioc_cgrp, cpd);
+}
+
+/*
+ * Scale @abs_cost to the inverse of @hw_inuse. The lower the hierarchical
+ * weight, the more expensive each IO. Must round up.
+ */
+static u64 abs_cost_to_cost(u64 abs_cost, u32 hw_inuse)
+{
+ return DIV64_U64_ROUND_UP(abs_cost * WEIGHT_ONE, hw_inuse);
+}
+
+/*
+ * The inverse of abs_cost_to_cost(). Must round up.
+ */
+static u64 cost_to_abs_cost(u64 cost, u32 hw_inuse)
+{
+ return DIV64_U64_ROUND_UP(cost * hw_inuse, WEIGHT_ONE);
+}
+
+static void iocg_commit_bio(struct ioc_gq *iocg, struct bio *bio,
+ u64 abs_cost, u64 cost)
+{
+ struct iocg_pcpu_stat *gcs;
+
+ bio->bi_iocost_cost = cost;
+ atomic64_add(cost, &iocg->vtime);
+
+ gcs = get_cpu_ptr(iocg->pcpu_stat);
+ local64_add(abs_cost, &gcs->abs_vusage);
+ put_cpu_ptr(gcs);
+}
+
+static void iocg_lock(struct ioc_gq *iocg, bool lock_ioc, unsigned long *flags)
+{
+ if (lock_ioc) {
+ spin_lock_irqsave(&iocg->ioc->lock, *flags);
+ spin_lock(&iocg->waitq.lock);
+ } else {
+ spin_lock_irqsave(&iocg->waitq.lock, *flags);
+ }
+}
+
+static void iocg_unlock(struct ioc_gq *iocg, bool unlock_ioc, unsigned long *flags)
+{
+ if (unlock_ioc) {
+ spin_unlock(&iocg->waitq.lock);
+ spin_unlock_irqrestore(&iocg->ioc->lock, *flags);
+ } else {
+ spin_unlock_irqrestore(&iocg->waitq.lock, *flags);
+ }
+}
+
+#define CREATE_TRACE_POINTS
+#include <trace/events/iocost.h>
+
+static void ioc_refresh_margins(struct ioc *ioc)
+{
+ struct ioc_margins *margins = &ioc->margins;
+ u32 period_us = ioc->period_us;
+ u64 vrate = ioc->vtime_base_rate;
+
+ margins->min = (period_us * MARGIN_MIN_PCT / 100) * vrate;
+ margins->low = (period_us * MARGIN_LOW_PCT / 100) * vrate;
+ margins->target = (period_us * MARGIN_TARGET_PCT / 100) * vrate;
+}
+
+/* latency Qos params changed, update period_us and all the dependent params */
+static void ioc_refresh_period_us(struct ioc *ioc)
+{
+ u32 ppm, lat, multi, period_us;
+
+ lockdep_assert_held(&ioc->lock);
+
+ /* pick the higher latency target */
+ if (ioc->params.qos[QOS_RLAT] >= ioc->params.qos[QOS_WLAT]) {
+ ppm = ioc->params.qos[QOS_RPPM];
+ lat = ioc->params.qos[QOS_RLAT];
+ } else {
+ ppm = ioc->params.qos[QOS_WPPM];
+ lat = ioc->params.qos[QOS_WLAT];
+ }
+
+ /*
+ * We want the period to be long enough to contain a healthy number
+ * of IOs while short enough for granular control. Define it as a
+ * multiple of the latency target. Ideally, the multiplier should
+ * be scaled according to the percentile so that it would nominally
+ * contain a certain number of requests. Let's be simpler and
+ * scale it linearly so that it's 2x >= pct(90) and 10x at pct(50).
+ */
+ if (ppm)
+ multi = max_t(u32, (MILLION - ppm) / 50000, 2);
+ else
+ multi = 2;
+ period_us = multi * lat;
+ period_us = clamp_t(u32, period_us, MIN_PERIOD, MAX_PERIOD);
+
+ /* calculate dependent params */
+ ioc->period_us = period_us;
+ ioc->timer_slack_ns = div64_u64(
+ (u64)period_us * NSEC_PER_USEC * TIMER_SLACK_PCT,
+ 100);
+ ioc_refresh_margins(ioc);
+}
+
+static int ioc_autop_idx(struct ioc *ioc)
+{
+ int idx = ioc->autop_idx;
+ const struct ioc_params *p = &autop[idx];
+ u32 vrate_pct;
+ u64 now_ns;
+
+ /* rotational? */
+ if (!blk_queue_nonrot(ioc->rqos.q))
+ return AUTOP_HDD;
+
+ /* handle SATA SSDs w/ broken NCQ */
+ if (blk_queue_depth(ioc->rqos.q) == 1)
+ return AUTOP_SSD_QD1;
+
+ /* use one of the normal ssd sets */
+ if (idx < AUTOP_SSD_DFL)
+ return AUTOP_SSD_DFL;
+
+ /* if user is overriding anything, maintain what was there */
+ if (ioc->user_qos_params || ioc->user_cost_model)
+ return idx;
+
+ /* step up/down based on the vrate */
+ vrate_pct = div64_u64(ioc->vtime_base_rate * 100, VTIME_PER_USEC);
+ now_ns = ktime_get_ns();
+
+ if (p->too_fast_vrate_pct && p->too_fast_vrate_pct <= vrate_pct) {
+ if (!ioc->autop_too_fast_at)
+ ioc->autop_too_fast_at = now_ns;
+ if (now_ns - ioc->autop_too_fast_at >= AUTOP_CYCLE_NSEC)
+ return idx + 1;
+ } else {
+ ioc->autop_too_fast_at = 0;
+ }
+
+ if (p->too_slow_vrate_pct && p->too_slow_vrate_pct >= vrate_pct) {
+ if (!ioc->autop_too_slow_at)
+ ioc->autop_too_slow_at = now_ns;
+ if (now_ns - ioc->autop_too_slow_at >= AUTOP_CYCLE_NSEC)
+ return idx - 1;
+ } else {
+ ioc->autop_too_slow_at = 0;
+ }
+
+ return idx;
+}
+
+/*
+ * Take the followings as input
+ *
+ * @bps maximum sequential throughput
+ * @seqiops maximum sequential 4k iops
+ * @randiops maximum random 4k iops
+ *
+ * and calculate the linear model cost coefficients.
+ *
+ * *@page per-page cost 1s / (@bps / 4096)
+ * *@seqio base cost of a seq IO max((1s / @seqiops) - *@page, 0)
+ * @randiops base cost of a rand IO max((1s / @randiops) - *@page, 0)
+ */
+static void calc_lcoefs(u64 bps, u64 seqiops, u64 randiops,
+ u64 *page, u64 *seqio, u64 *randio)
+{
+ u64 v;
+
+ *page = *seqio = *randio = 0;
+
+ if (bps) {
+ u64 bps_pages = DIV_ROUND_UP_ULL(bps, IOC_PAGE_SIZE);
+
+ if (bps_pages)
+ *page = DIV64_U64_ROUND_UP(VTIME_PER_SEC, bps_pages);
+ else
+ *page = 1;
+ }
+
+ if (seqiops) {
+ v = DIV64_U64_ROUND_UP(VTIME_PER_SEC, seqiops);
+ if (v > *page)
+ *seqio = v - *page;
+ }
+
+ if (randiops) {
+ v = DIV64_U64_ROUND_UP(VTIME_PER_SEC, randiops);
+ if (v > *page)
+ *randio = v - *page;
+ }
+}
+
+static void ioc_refresh_lcoefs(struct ioc *ioc)
+{
+ u64 *u = ioc->params.i_lcoefs;
+ u64 *c = ioc->params.lcoefs;
+
+ calc_lcoefs(u[I_LCOEF_RBPS], u[I_LCOEF_RSEQIOPS], u[I_LCOEF_RRANDIOPS],
+ &c[LCOEF_RPAGE], &c[LCOEF_RSEQIO], &c[LCOEF_RRANDIO]);
+ calc_lcoefs(u[I_LCOEF_WBPS], u[I_LCOEF_WSEQIOPS], u[I_LCOEF_WRANDIOPS],
+ &c[LCOEF_WPAGE], &c[LCOEF_WSEQIO], &c[LCOEF_WRANDIO]);
+}
+
+static bool ioc_refresh_params(struct ioc *ioc, bool force)
+{
+ const struct ioc_params *p;
+ int idx;
+
+ lockdep_assert_held(&ioc->lock);
+
+ idx = ioc_autop_idx(ioc);
+ p = &autop[idx];
+
+ if (idx == ioc->autop_idx && !force)
+ return false;
+
+ if (idx != ioc->autop_idx)
+ atomic64_set(&ioc->vtime_rate, VTIME_PER_USEC);
+
+ ioc->autop_idx = idx;
+ ioc->autop_too_fast_at = 0;
+ ioc->autop_too_slow_at = 0;
+
+ if (!ioc->user_qos_params)
+ memcpy(ioc->params.qos, p->qos, sizeof(p->qos));
+ if (!ioc->user_cost_model)
+ memcpy(ioc->params.i_lcoefs, p->i_lcoefs, sizeof(p->i_lcoefs));
+
+ ioc_refresh_period_us(ioc);
+ ioc_refresh_lcoefs(ioc);
+
+ ioc->vrate_min = DIV64_U64_ROUND_UP((u64)ioc->params.qos[QOS_MIN] *
+ VTIME_PER_USEC, MILLION);
+ ioc->vrate_max = div64_u64((u64)ioc->params.qos[QOS_MAX] *
+ VTIME_PER_USEC, MILLION);
+
+ return true;
+}
+
+/*
+ * When an iocg accumulates too much vtime or gets deactivated, we throw away
+ * some vtime, which lowers the overall device utilization. As the exact amount
+ * which is being thrown away is known, we can compensate by accelerating the
+ * vrate accordingly so that the extra vtime generated in the current period
+ * matches what got lost.
+ */
+static void ioc_refresh_vrate(struct ioc *ioc, struct ioc_now *now)
+{
+ s64 pleft = ioc->period_at + ioc->period_us - now->now;
+ s64 vperiod = ioc->period_us * ioc->vtime_base_rate;
+ s64 vcomp, vcomp_min, vcomp_max;
+
+ lockdep_assert_held(&ioc->lock);
+
+ /* we need some time left in this period */
+ if (pleft <= 0)
+ goto done;
+
+ /*
+ * Calculate how much vrate should be adjusted to offset the error.
+ * Limit the amount of adjustment and deduct the adjusted amount from
+ * the error.
+ */
+ vcomp = -div64_s64(ioc->vtime_err, pleft);
+ vcomp_min = -(ioc->vtime_base_rate >> 1);
+ vcomp_max = ioc->vtime_base_rate;
+ vcomp = clamp(vcomp, vcomp_min, vcomp_max);
+
+ ioc->vtime_err += vcomp * pleft;
+
+ atomic64_set(&ioc->vtime_rate, ioc->vtime_base_rate + vcomp);
+done:
+ /* bound how much error can accumulate */
+ ioc->vtime_err = clamp(ioc->vtime_err, -vperiod, vperiod);
+}
+
+/* take a snapshot of the current [v]time and vrate */
+static void ioc_now(struct ioc *ioc, struct ioc_now *now)
+{
+ unsigned seq;
+
+ now->now_ns = ktime_get();
+ now->now = ktime_to_us(now->now_ns);
+ now->vrate = atomic64_read(&ioc->vtime_rate);
+
+ /*
+ * The current vtime is
+ *
+ * vtime at period start + (wallclock time since the start) * vrate
+ *
+ * As a consistent snapshot of `period_at_vtime` and `period_at` is
+ * needed, they're seqcount protected.
+ */
+ do {
+ seq = read_seqcount_begin(&ioc->period_seqcount);
+ now->vnow = ioc->period_at_vtime +
+ (now->now - ioc->period_at) * now->vrate;
+ } while (read_seqcount_retry(&ioc->period_seqcount, seq));
+}
+
+static void ioc_start_period(struct ioc *ioc, struct ioc_now *now)
+{
+ WARN_ON_ONCE(ioc->running != IOC_RUNNING);
+
+ write_seqcount_begin(&ioc->period_seqcount);
+ ioc->period_at = now->now;
+ ioc->period_at_vtime = now->vnow;
+ write_seqcount_end(&ioc->period_seqcount);
+
+ ioc->timer.expires = jiffies + usecs_to_jiffies(ioc->period_us);
+ add_timer(&ioc->timer);
+}
+
+/*
+ * Update @iocg's `active` and `inuse` to @active and @inuse, update level
+ * weight sums and propagate upwards accordingly. If @save, the current margin
+ * is saved to be used as reference for later inuse in-period adjustments.
+ */
+static void __propagate_weights(struct ioc_gq *iocg, u32 active, u32 inuse,
+ bool save, struct ioc_now *now)
+{
+ struct ioc *ioc = iocg->ioc;
+ int lvl;
+
+ lockdep_assert_held(&ioc->lock);
+
+ /*
+ * For an active leaf node, its inuse shouldn't be zero or exceed
+ * @active. An active internal node's inuse is solely determined by the
+ * inuse to active ratio of its children regardless of @inuse.
+ */
+ if (list_empty(&iocg->active_list) && iocg->child_active_sum) {
+ inuse = DIV64_U64_ROUND_UP(active * iocg->child_inuse_sum,
+ iocg->child_active_sum);
+ } else {
+ inuse = clamp_t(u32, inuse, 1, active);
+ }
+
+ iocg->last_inuse = iocg->inuse;
+ if (save)
+ iocg->saved_margin = now->vnow - atomic64_read(&iocg->vtime);
+
+ if (active == iocg->active && inuse == iocg->inuse)
+ return;
+
+ for (lvl = iocg->level - 1; lvl >= 0; lvl--) {
+ struct ioc_gq *parent = iocg->ancestors[lvl];
+ struct ioc_gq *child = iocg->ancestors[lvl + 1];
+ u32 parent_active = 0, parent_inuse = 0;
+
+ /* update the level sums */
+ parent->child_active_sum += (s32)(active - child->active);
+ parent->child_inuse_sum += (s32)(inuse - child->inuse);
+ /* apply the updates */
+ child->active = active;
+ child->inuse = inuse;
+
+ /*
+ * The delta between inuse and active sums indicates that
+ * that much of weight is being given away. Parent's inuse
+ * and active should reflect the ratio.
+ */
+ if (parent->child_active_sum) {
+ parent_active = parent->weight;
+ parent_inuse = DIV64_U64_ROUND_UP(
+ parent_active * parent->child_inuse_sum,
+ parent->child_active_sum);
+ }
+
+ /* do we need to keep walking up? */
+ if (parent_active == parent->active &&
+ parent_inuse == parent->inuse)
+ break;
+
+ active = parent_active;
+ inuse = parent_inuse;
+ }
+
+ ioc->weights_updated = true;
+}
+
+static void commit_weights(struct ioc *ioc)
+{
+ lockdep_assert_held(&ioc->lock);
+
+ if (ioc->weights_updated) {
+ /* paired with rmb in current_hweight(), see there */
+ smp_wmb();
+ atomic_inc(&ioc->hweight_gen);
+ ioc->weights_updated = false;
+ }
+}
+
+static void propagate_weights(struct ioc_gq *iocg, u32 active, u32 inuse,
+ bool save, struct ioc_now *now)
+{
+ __propagate_weights(iocg, active, inuse, save, now);
+ commit_weights(iocg->ioc);
+}
+
+static void current_hweight(struct ioc_gq *iocg, u32 *hw_activep, u32 *hw_inusep)
+{
+ struct ioc *ioc = iocg->ioc;
+ int lvl;
+ u32 hwa, hwi;
+ int ioc_gen;
+
+ /* hot path - if uptodate, use cached */
+ ioc_gen = atomic_read(&ioc->hweight_gen);
+ if (ioc_gen == iocg->hweight_gen)
+ goto out;
+
+ /*
+ * Paired with wmb in commit_weights(). If we saw the updated
+ * hweight_gen, all the weight updates from __propagate_weights() are
+ * visible too.
+ *
+ * We can race with weight updates during calculation and get it
+ * wrong. However, hweight_gen would have changed and a future
+ * reader will recalculate and we're guaranteed to discard the
+ * wrong result soon.
+ */
+ smp_rmb();
+
+ hwa = hwi = WEIGHT_ONE;
+ for (lvl = 0; lvl <= iocg->level - 1; lvl++) {
+ struct ioc_gq *parent = iocg->ancestors[lvl];
+ struct ioc_gq *child = iocg->ancestors[lvl + 1];
+ u64 active_sum = READ_ONCE(parent->child_active_sum);
+ u64 inuse_sum = READ_ONCE(parent->child_inuse_sum);
+ u32 active = READ_ONCE(child->active);
+ u32 inuse = READ_ONCE(child->inuse);
+
+ /* we can race with deactivations and either may read as zero */
+ if (!active_sum || !inuse_sum)
+ continue;
+
+ active_sum = max_t(u64, active, active_sum);
+ hwa = div64_u64((u64)hwa * active, active_sum);
+
+ inuse_sum = max_t(u64, inuse, inuse_sum);
+ hwi = div64_u64((u64)hwi * inuse, inuse_sum);
+ }
+
+ iocg->hweight_active = max_t(u32, hwa, 1);
+ iocg->hweight_inuse = max_t(u32, hwi, 1);
+ iocg->hweight_gen = ioc_gen;
+out:
+ if (hw_activep)
+ *hw_activep = iocg->hweight_active;
+ if (hw_inusep)
+ *hw_inusep = iocg->hweight_inuse;
+}
+
+/*
+ * Calculate the hweight_inuse @iocg would get with max @inuse assuming all the
+ * other weights stay unchanged.
+ */
+static u32 current_hweight_max(struct ioc_gq *iocg)
+{
+ u32 hwm = WEIGHT_ONE;
+ u32 inuse = iocg->active;
+ u64 child_inuse_sum;
+ int lvl;
+
+ lockdep_assert_held(&iocg->ioc->lock);
+
+ for (lvl = iocg->level - 1; lvl >= 0; lvl--) {
+ struct ioc_gq *parent = iocg->ancestors[lvl];
+ struct ioc_gq *child = iocg->ancestors[lvl + 1];
+
+ child_inuse_sum = parent->child_inuse_sum + inuse - child->inuse;
+ hwm = div64_u64((u64)hwm * inuse, child_inuse_sum);
+ inuse = DIV64_U64_ROUND_UP(parent->active * child_inuse_sum,
+ parent->child_active_sum);
+ }
+
+ return max_t(u32, hwm, 1);
+}
+
+static void weight_updated(struct ioc_gq *iocg, struct ioc_now *now)
+{
+ struct ioc *ioc = iocg->ioc;
+ struct blkcg_gq *blkg = iocg_to_blkg(iocg);
+ struct ioc_cgrp *iocc = blkcg_to_iocc(blkg->blkcg);
+ u32 weight;
+
+ lockdep_assert_held(&ioc->lock);
+
+ weight = iocg->cfg_weight ?: iocc->dfl_weight;
+ if (weight != iocg->weight && iocg->active)
+ propagate_weights(iocg, weight, iocg->inuse, true, now);
+ iocg->weight = weight;
+}
+
+static bool iocg_activate(struct ioc_gq *iocg, struct ioc_now *now)
+{
+ struct ioc *ioc = iocg->ioc;
+ u64 last_period, cur_period;
+ u64 vtime, vtarget;
+ int i;
+
+ /*
+ * If seem to be already active, just update the stamp to tell the
+ * timer that we're still active. We don't mind occassional races.
+ */
+ if (!list_empty(&iocg->active_list)) {
+ ioc_now(ioc, now);
+ cur_period = atomic64_read(&ioc->cur_period);
+ if (atomic64_read(&iocg->active_period) != cur_period)
+ atomic64_set(&iocg->active_period, cur_period);
+ return true;
+ }
+
+ /* racy check on internal node IOs, treat as root level IOs */
+ if (iocg->child_active_sum)
+ return false;
+
+ spin_lock_irq(&ioc->lock);
+
+ ioc_now(ioc, now);
+
+ /* update period */
+ cur_period = atomic64_read(&ioc->cur_period);
+ last_period = atomic64_read(&iocg->active_period);
+ atomic64_set(&iocg->active_period, cur_period);
+
+ /* already activated or breaking leaf-only constraint? */
+ if (!list_empty(&iocg->active_list))
+ goto succeed_unlock;
+ for (i = iocg->level - 1; i > 0; i--)
+ if (!list_empty(&iocg->ancestors[i]->active_list))
+ goto fail_unlock;
+
+ if (iocg->child_active_sum)
+ goto fail_unlock;
+
+ /*
+ * Always start with the target budget. On deactivation, we throw away
+ * anything above it.
+ */
+ vtarget = now->vnow - ioc->margins.target;
+ vtime = atomic64_read(&iocg->vtime);
+
+ atomic64_add(vtarget - vtime, &iocg->vtime);
+ atomic64_add(vtarget - vtime, &iocg->done_vtime);
+ vtime = vtarget;
+
+ /*
+ * Activate, propagate weight and start period timer if not
+ * running. Reset hweight_gen to avoid accidental match from
+ * wrapping.
+ */
+ iocg->hweight_gen = atomic_read(&ioc->hweight_gen) - 1;
+ list_add(&iocg->active_list, &ioc->active_iocgs);
+
+ propagate_weights(iocg, iocg->weight,
+ iocg->last_inuse ?: iocg->weight, true, now);
+
+ TRACE_IOCG_PATH(iocg_activate, iocg, now,
+ last_period, cur_period, vtime);
+
+ iocg->activated_at = now->now;
+
+ if (ioc->running == IOC_IDLE) {
+ ioc->running = IOC_RUNNING;
+ ioc->dfgv_period_at = now->now;
+ ioc->dfgv_period_rem = 0;
+ ioc_start_period(ioc, now);
+ }
+
+succeed_unlock:
+ spin_unlock_irq(&ioc->lock);
+ return true;
+
+fail_unlock:
+ spin_unlock_irq(&ioc->lock);
+ return false;
+}
+
+static bool iocg_kick_delay(struct ioc_gq *iocg, struct ioc_now *now)
+{
+ struct ioc *ioc = iocg->ioc;
+ struct blkcg_gq *blkg = iocg_to_blkg(iocg);
+ u64 tdelta, delay, new_delay;
+ s64 vover, vover_pct;
+ u32 hwa;
+
+ lockdep_assert_held(&iocg->waitq.lock);
+
+ /* calculate the current delay in effect - 1/2 every second */
+ tdelta = now->now - iocg->delay_at;
+ if (iocg->delay)
+ delay = iocg->delay >> div64_u64(tdelta, USEC_PER_SEC);
+ else
+ delay = 0;
+
+ /* calculate the new delay from the debt amount */
+ current_hweight(iocg, &hwa, NULL);
+ vover = atomic64_read(&iocg->vtime) +
+ abs_cost_to_cost(iocg->abs_vdebt, hwa) - now->vnow;
+ vover_pct = div64_s64(100 * vover,
+ ioc->period_us * ioc->vtime_base_rate);
+
+ if (vover_pct <= MIN_DELAY_THR_PCT)
+ new_delay = 0;
+ else if (vover_pct >= MAX_DELAY_THR_PCT)
+ new_delay = MAX_DELAY;
+ else
+ new_delay = MIN_DELAY +
+ div_u64((MAX_DELAY - MIN_DELAY) *
+ (vover_pct - MIN_DELAY_THR_PCT),
+ MAX_DELAY_THR_PCT - MIN_DELAY_THR_PCT);
+
+ /* pick the higher one and apply */
+ if (new_delay > delay) {
+ iocg->delay = new_delay;
+ iocg->delay_at = now->now;
+ delay = new_delay;
+ }
+
+ if (delay >= MIN_DELAY) {
+ if (!iocg->indelay_since)
+ iocg->indelay_since = now->now;
+ blkcg_set_delay(blkg, delay * NSEC_PER_USEC);
+ return true;
+ } else {
+ if (iocg->indelay_since) {
+ iocg->local_stat.indelay_us += now->now - iocg->indelay_since;
+ iocg->indelay_since = 0;
+ }
+ iocg->delay = 0;
+ blkcg_clear_delay(blkg);
+ return false;
+ }
+}
+
+static void iocg_incur_debt(struct ioc_gq *iocg, u64 abs_cost,
+ struct ioc_now *now)
+{
+ struct iocg_pcpu_stat *gcs;
+
+ lockdep_assert_held(&iocg->ioc->lock);
+ lockdep_assert_held(&iocg->waitq.lock);
+ WARN_ON_ONCE(list_empty(&iocg->active_list));
+
+ /*
+ * Once in debt, debt handling owns inuse. @iocg stays at the minimum
+ * inuse donating all of it share to others until its debt is paid off.
+ */
+ if (!iocg->abs_vdebt && abs_cost) {
+ iocg->indebt_since = now->now;
+ propagate_weights(iocg, iocg->active, 0, false, now);
+ }
+
+ iocg->abs_vdebt += abs_cost;
+
+ gcs = get_cpu_ptr(iocg->pcpu_stat);
+ local64_add(abs_cost, &gcs->abs_vusage);
+ put_cpu_ptr(gcs);
+}
+
+static void iocg_pay_debt(struct ioc_gq *iocg, u64 abs_vpay,
+ struct ioc_now *now)
+{
+ lockdep_assert_held(&iocg->ioc->lock);
+ lockdep_assert_held(&iocg->waitq.lock);
+
+ /* make sure that nobody messed with @iocg */
+ WARN_ON_ONCE(list_empty(&iocg->active_list));
+ WARN_ON_ONCE(iocg->inuse > 1);
+
+ iocg->abs_vdebt -= min(abs_vpay, iocg->abs_vdebt);
+
+ /* if debt is paid in full, restore inuse */
+ if (!iocg->abs_vdebt) {
+ iocg->local_stat.indebt_us += now->now - iocg->indebt_since;
+ iocg->indebt_since = 0;
+
+ propagate_weights(iocg, iocg->active, iocg->last_inuse,
+ false, now);
+ }
+}
+
+static int iocg_wake_fn(struct wait_queue_entry *wq_entry, unsigned mode,
+ int flags, void *key)
+{
+ struct iocg_wait *wait = container_of(wq_entry, struct iocg_wait, wait);
+ struct iocg_wake_ctx *ctx = (struct iocg_wake_ctx *)key;
+ u64 cost = abs_cost_to_cost(wait->abs_cost, ctx->hw_inuse);
+
+ ctx->vbudget -= cost;
+
+ if (ctx->vbudget < 0)
+ return -1;
+
+ iocg_commit_bio(ctx->iocg, wait->bio, wait->abs_cost, cost);
+ wait->committed = true;
+
+ /*
+ * autoremove_wake_function() removes the wait entry only when it
+ * actually changed the task state. We want the wait always removed.
+ * Remove explicitly and use default_wake_function(). Note that the
+ * order of operations is important as finish_wait() tests whether
+ * @wq_entry is removed without grabbing the lock.
+ */
+ default_wake_function(wq_entry, mode, flags, key);
+ list_del_init_careful(&wq_entry->entry);
+ return 0;
+}
+
+/*
+ * Calculate the accumulated budget, pay debt if @pay_debt and wake up waiters
+ * accordingly. When @pay_debt is %true, the caller must be holding ioc->lock in
+ * addition to iocg->waitq.lock.
+ */
+static void iocg_kick_waitq(struct ioc_gq *iocg, bool pay_debt,
+ struct ioc_now *now)
+{
+ struct ioc *ioc = iocg->ioc;
+ struct iocg_wake_ctx ctx = { .iocg = iocg };
+ u64 vshortage, expires, oexpires;
+ s64 vbudget;
+ u32 hwa;
+
+ lockdep_assert_held(&iocg->waitq.lock);
+
+ current_hweight(iocg, &hwa, NULL);
+ vbudget = now->vnow - atomic64_read(&iocg->vtime);
+
+ /* pay off debt */
+ if (pay_debt && iocg->abs_vdebt && vbudget > 0) {
+ u64 abs_vbudget = cost_to_abs_cost(vbudget, hwa);
+ u64 abs_vpay = min_t(u64, abs_vbudget, iocg->abs_vdebt);
+ u64 vpay = abs_cost_to_cost(abs_vpay, hwa);
+
+ lockdep_assert_held(&ioc->lock);
+
+ atomic64_add(vpay, &iocg->vtime);
+ atomic64_add(vpay, &iocg->done_vtime);
+ iocg_pay_debt(iocg, abs_vpay, now);
+ vbudget -= vpay;
+ }
+
+ if (iocg->abs_vdebt || iocg->delay)
+ iocg_kick_delay(iocg, now);
+
+ /*
+ * Debt can still be outstanding if we haven't paid all yet or the
+ * caller raced and called without @pay_debt. Shouldn't wake up waiters
+ * under debt. Make sure @vbudget reflects the outstanding amount and is
+ * not positive.
+ */
+ if (iocg->abs_vdebt) {
+ s64 vdebt = abs_cost_to_cost(iocg->abs_vdebt, hwa);
+ vbudget = min_t(s64, 0, vbudget - vdebt);
+ }
+
+ /*
+ * Wake up the ones which are due and see how much vtime we'll need for
+ * the next one. As paying off debt restores hw_inuse, it must be read
+ * after the above debt payment.
+ */
+ ctx.vbudget = vbudget;
+ current_hweight(iocg, NULL, &ctx.hw_inuse);
+
+ __wake_up_locked_key(&iocg->waitq, TASK_NORMAL, &ctx);
+
+ if (!waitqueue_active(&iocg->waitq)) {
+ if (iocg->wait_since) {
+ iocg->local_stat.wait_us += now->now - iocg->wait_since;
+ iocg->wait_since = 0;
+ }
+ return;
+ }
+
+ if (!iocg->wait_since)
+ iocg->wait_since = now->now;
+
+ if (WARN_ON_ONCE(ctx.vbudget >= 0))
+ return;
+
+ /* determine next wakeup, add a timer margin to guarantee chunking */
+ vshortage = -ctx.vbudget;
+ expires = now->now_ns +
+ DIV64_U64_ROUND_UP(vshortage, ioc->vtime_base_rate) *
+ NSEC_PER_USEC;
+ expires += ioc->timer_slack_ns;
+
+ /* if already active and close enough, don't bother */
+ oexpires = ktime_to_ns(hrtimer_get_softexpires(&iocg->waitq_timer));
+ if (hrtimer_is_queued(&iocg->waitq_timer) &&
+ abs(oexpires - expires) <= ioc->timer_slack_ns)
+ return;
+
+ hrtimer_start_range_ns(&iocg->waitq_timer, ns_to_ktime(expires),
+ ioc->timer_slack_ns, HRTIMER_MODE_ABS);
+}
+
+static enum hrtimer_restart iocg_waitq_timer_fn(struct hrtimer *timer)
+{
+ struct ioc_gq *iocg = container_of(timer, struct ioc_gq, waitq_timer);
+ bool pay_debt = READ_ONCE(iocg->abs_vdebt);
+ struct ioc_now now;
+ unsigned long flags;
+
+ ioc_now(iocg->ioc, &now);
+
+ iocg_lock(iocg, pay_debt, &flags);
+ iocg_kick_waitq(iocg, pay_debt, &now);
+ iocg_unlock(iocg, pay_debt, &flags);
+
+ return HRTIMER_NORESTART;
+}
+
+static void ioc_lat_stat(struct ioc *ioc, u32 *missed_ppm_ar, u32 *rq_wait_pct_p)
+{
+ u32 nr_met[2] = { };
+ u32 nr_missed[2] = { };
+ u64 rq_wait_ns = 0;
+ int cpu, rw;
+
+ for_each_online_cpu(cpu) {
+ struct ioc_pcpu_stat *stat = per_cpu_ptr(ioc->pcpu_stat, cpu);
+ u64 this_rq_wait_ns;
+
+ for (rw = READ; rw <= WRITE; rw++) {
+ u32 this_met = local_read(&stat->missed[rw].nr_met);
+ u32 this_missed = local_read(&stat->missed[rw].nr_missed);
+
+ nr_met[rw] += this_met - stat->missed[rw].last_met;
+ nr_missed[rw] += this_missed - stat->missed[rw].last_missed;
+ stat->missed[rw].last_met = this_met;
+ stat->missed[rw].last_missed = this_missed;
+ }
+
+ this_rq_wait_ns = local64_read(&stat->rq_wait_ns);
+ rq_wait_ns += this_rq_wait_ns - stat->last_rq_wait_ns;
+ stat->last_rq_wait_ns = this_rq_wait_ns;
+ }
+
+ for (rw = READ; rw <= WRITE; rw++) {
+ if (nr_met[rw] + nr_missed[rw])
+ missed_ppm_ar[rw] =
+ DIV64_U64_ROUND_UP((u64)nr_missed[rw] * MILLION,
+ nr_met[rw] + nr_missed[rw]);
+ else
+ missed_ppm_ar[rw] = 0;
+ }
+
+ *rq_wait_pct_p = div64_u64(rq_wait_ns * 100,
+ ioc->period_us * NSEC_PER_USEC);
+}
+
+/* was iocg idle this period? */
+static bool iocg_is_idle(struct ioc_gq *iocg)
+{
+ struct ioc *ioc = iocg->ioc;
+
+ /* did something get issued this period? */
+ if (atomic64_read(&iocg->active_period) ==
+ atomic64_read(&ioc->cur_period))
+ return false;
+
+ /* is something in flight? */
+ if (atomic64_read(&iocg->done_vtime) != atomic64_read(&iocg->vtime))
+ return false;
+
+ return true;
+}
+
+/*
+ * Call this function on the target leaf @iocg's to build pre-order traversal
+ * list of all the ancestors in @inner_walk. The inner nodes are linked through
+ * ->walk_list and the caller is responsible for dissolving the list after use.
+ */
+static void iocg_build_inner_walk(struct ioc_gq *iocg,
+ struct list_head *inner_walk)
+{
+ int lvl;
+
+ WARN_ON_ONCE(!list_empty(&iocg->walk_list));
+
+ /* find the first ancestor which hasn't been visited yet */
+ for (lvl = iocg->level - 1; lvl >= 0; lvl--) {
+ if (!list_empty(&iocg->ancestors[lvl]->walk_list))
+ break;
+ }
+
+ /* walk down and visit the inner nodes to get pre-order traversal */
+ while (++lvl <= iocg->level - 1) {
+ struct ioc_gq *inner = iocg->ancestors[lvl];
+
+ /* record traversal order */
+ list_add_tail(&inner->walk_list, inner_walk);
+ }
+}
+
+/* collect per-cpu counters and propagate the deltas to the parent */
+static void iocg_flush_stat_one(struct ioc_gq *iocg, struct ioc_now *now)
+{
+ struct ioc *ioc = iocg->ioc;
+ struct iocg_stat new_stat;
+ u64 abs_vusage = 0;
+ u64 vusage_delta;
+ int cpu;
+
+ lockdep_assert_held(&iocg->ioc->lock);
+
+ /* collect per-cpu counters */
+ for_each_possible_cpu(cpu) {
+ abs_vusage += local64_read(
+ per_cpu_ptr(&iocg->pcpu_stat->abs_vusage, cpu));
+ }
+ vusage_delta = abs_vusage - iocg->last_stat_abs_vusage;
+ iocg->last_stat_abs_vusage = abs_vusage;
+
+ iocg->usage_delta_us = div64_u64(vusage_delta, ioc->vtime_base_rate);
+ iocg->local_stat.usage_us += iocg->usage_delta_us;
+
+ /* propagate upwards */
+ new_stat.usage_us =
+ iocg->local_stat.usage_us + iocg->desc_stat.usage_us;
+ new_stat.wait_us =
+ iocg->local_stat.wait_us + iocg->desc_stat.wait_us;
+ new_stat.indebt_us =
+ iocg->local_stat.indebt_us + iocg->desc_stat.indebt_us;
+ new_stat.indelay_us =
+ iocg->local_stat.indelay_us + iocg->desc_stat.indelay_us;
+
+ /* propagate the deltas to the parent */
+ if (iocg->level > 0) {
+ struct iocg_stat *parent_stat =
+ &iocg->ancestors[iocg->level - 1]->desc_stat;
+
+ parent_stat->usage_us +=
+ new_stat.usage_us - iocg->last_stat.usage_us;
+ parent_stat->wait_us +=
+ new_stat.wait_us - iocg->last_stat.wait_us;
+ parent_stat->indebt_us +=
+ new_stat.indebt_us - iocg->last_stat.indebt_us;
+ parent_stat->indelay_us +=
+ new_stat.indelay_us - iocg->last_stat.indelay_us;
+ }
+
+ iocg->last_stat = new_stat;
+}
+
+/* get stat counters ready for reading on all active iocgs */
+static void iocg_flush_stat(struct list_head *target_iocgs, struct ioc_now *now)
+{
+ LIST_HEAD(inner_walk);
+ struct ioc_gq *iocg, *tiocg;
+
+ /* flush leaves and build inner node walk list */
+ list_for_each_entry(iocg, target_iocgs, active_list) {
+ iocg_flush_stat_one(iocg, now);
+ iocg_build_inner_walk(iocg, &inner_walk);
+ }
+
+ /* keep flushing upwards by walking the inner list backwards */
+ list_for_each_entry_safe_reverse(iocg, tiocg, &inner_walk, walk_list) {
+ iocg_flush_stat_one(iocg, now);
+ list_del_init(&iocg->walk_list);
+ }
+}
+
+/*
+ * Determine what @iocg's hweight_inuse should be after donating unused
+ * capacity. @hwm is the upper bound and used to signal no donation. This
+ * function also throws away @iocg's excess budget.
+ */
+static u32 hweight_after_donation(struct ioc_gq *iocg, u32 old_hwi, u32 hwm,
+ u32 usage, struct ioc_now *now)
+{
+ struct ioc *ioc = iocg->ioc;
+ u64 vtime = atomic64_read(&iocg->vtime);
+ s64 excess, delta, target, new_hwi;
+
+ /* debt handling owns inuse for debtors */
+ if (iocg->abs_vdebt)
+ return 1;
+
+ /* see whether minimum margin requirement is met */
+ if (waitqueue_active(&iocg->waitq) ||
+ time_after64(vtime, now->vnow - ioc->margins.min))
+ return hwm;
+
+ /* throw away excess above target */
+ excess = now->vnow - vtime - ioc->margins.target;
+ if (excess > 0) {
+ atomic64_add(excess, &iocg->vtime);
+ atomic64_add(excess, &iocg->done_vtime);
+ vtime += excess;
+ ioc->vtime_err -= div64_u64(excess * old_hwi, WEIGHT_ONE);
+ }
+
+ /*
+ * Let's say the distance between iocg's and device's vtimes as a
+ * fraction of period duration is delta. Assuming that the iocg will
+ * consume the usage determined above, we want to determine new_hwi so
+ * that delta equals MARGIN_TARGET at the end of the next period.
+ *
+ * We need to execute usage worth of IOs while spending the sum of the
+ * new budget (1 - MARGIN_TARGET) and the leftover from the last period
+ * (delta):
+ *
+ * usage = (1 - MARGIN_TARGET + delta) * new_hwi
+ *
+ * Therefore, the new_hwi is:
+ *
+ * new_hwi = usage / (1 - MARGIN_TARGET + delta)
+ */
+ delta = div64_s64(WEIGHT_ONE * (now->vnow - vtime),
+ now->vnow - ioc->period_at_vtime);
+ target = WEIGHT_ONE * MARGIN_TARGET_PCT / 100;
+ new_hwi = div64_s64(WEIGHT_ONE * usage, WEIGHT_ONE - target + delta);
+
+ return clamp_t(s64, new_hwi, 1, hwm);
+}
+
+/*
+ * For work-conservation, an iocg which isn't using all of its share should
+ * donate the leftover to other iocgs. There are two ways to achieve this - 1.
+ * bumping up vrate accordingly 2. lowering the donating iocg's inuse weight.
+ *
+ * #1 is mathematically simpler but has the drawback of requiring synchronous
+ * global hweight_inuse updates when idle iocg's get activated or inuse weights
+ * change due to donation snapbacks as it has the possibility of grossly
+ * overshooting what's allowed by the model and vrate.
+ *
+ * #2 is inherently safe with local operations. The donating iocg can easily
+ * snap back to higher weights when needed without worrying about impacts on
+ * other nodes as the impacts will be inherently correct. This also makes idle
+ * iocg activations safe. The only effect activations have is decreasing
+ * hweight_inuse of others, the right solution to which is for those iocgs to
+ * snap back to higher weights.
+ *
+ * So, we go with #2. The challenge is calculating how each donating iocg's
+ * inuse should be adjusted to achieve the target donation amounts. This is done
+ * using Andy's method described in the following pdf.
+ *
+ * https://drive.google.com/file/d/1PsJwxPFtjUnwOY1QJ5AeICCcsL7BM3bo
+ *
+ * Given the weights and target after-donation hweight_inuse values, Andy's
+ * method determines how the proportional distribution should look like at each
+ * sibling level to maintain the relative relationship between all non-donating
+ * pairs. To roughly summarize, it divides the tree into donating and
+ * non-donating parts, calculates global donation rate which is used to
+ * determine the target hweight_inuse for each node, and then derives per-level
+ * proportions.
+ *
+ * The following pdf shows that global distribution calculated this way can be
+ * achieved by scaling inuse weights of donating leaves and propagating the
+ * adjustments upwards proportionally.
+ *
+ * https://drive.google.com/file/d/1vONz1-fzVO7oY5DXXsLjSxEtYYQbOvsE
+ *
+ * Combining the above two, we can determine how each leaf iocg's inuse should
+ * be adjusted to achieve the target donation.
+ *
+ * https://drive.google.com/file/d/1WcrltBOSPN0qXVdBgnKm4mdp9FhuEFQN
+ *
+ * The inline comments use symbols from the last pdf.
+ *
+ * b is the sum of the absolute budgets in the subtree. 1 for the root node.
+ * f is the sum of the absolute budgets of non-donating nodes in the subtree.
+ * t is the sum of the absolute budgets of donating nodes in the subtree.
+ * w is the weight of the node. w = w_f + w_t
+ * w_f is the non-donating portion of w. w_f = w * f / b
+ * w_b is the donating portion of w. w_t = w * t / b
+ * s is the sum of all sibling weights. s = Sum(w) for siblings
+ * s_f and s_t are the non-donating and donating portions of s.
+ *
+ * Subscript p denotes the parent's counterpart and ' the adjusted value - e.g.
+ * w_pt is the donating portion of the parent's weight and w'_pt the same value
+ * after adjustments. Subscript r denotes the root node's values.
+ */
+static void transfer_surpluses(struct list_head *surpluses, struct ioc_now *now)
+{
+ LIST_HEAD(over_hwa);
+ LIST_HEAD(inner_walk);
+ struct ioc_gq *iocg, *tiocg, *root_iocg;
+ u32 after_sum, over_sum, over_target, gamma;
+
+ /*
+ * It's pretty unlikely but possible for the total sum of
+ * hweight_after_donation's to be higher than WEIGHT_ONE, which will
+ * confuse the following calculations. If such condition is detected,
+ * scale down everyone over its full share equally to keep the sum below
+ * WEIGHT_ONE.
+ */
+ after_sum = 0;
+ over_sum = 0;
+ list_for_each_entry(iocg, surpluses, surplus_list) {
+ u32 hwa;
+
+ current_hweight(iocg, &hwa, NULL);
+ after_sum += iocg->hweight_after_donation;
+
+ if (iocg->hweight_after_donation > hwa) {
+ over_sum += iocg->hweight_after_donation;
+ list_add(&iocg->walk_list, &over_hwa);
+ }
+ }
+
+ if (after_sum >= WEIGHT_ONE) {
+ /*
+ * The delta should be deducted from the over_sum, calculate
+ * target over_sum value.
+ */
+ u32 over_delta = after_sum - (WEIGHT_ONE - 1);
+ WARN_ON_ONCE(over_sum <= over_delta);
+ over_target = over_sum - over_delta;
+ } else {
+ over_target = 0;
+ }
+
+ list_for_each_entry_safe(iocg, tiocg, &over_hwa, walk_list) {
+ if (over_target)
+ iocg->hweight_after_donation =
+ div_u64((u64)iocg->hweight_after_donation *
+ over_target, over_sum);
+ list_del_init(&iocg->walk_list);
+ }
+
+ /*
+ * Build pre-order inner node walk list and prepare for donation
+ * adjustment calculations.
+ */
+ list_for_each_entry(iocg, surpluses, surplus_list) {
+ iocg_build_inner_walk(iocg, &inner_walk);
+ }
+
+ root_iocg = list_first_entry(&inner_walk, struct ioc_gq, walk_list);
+ WARN_ON_ONCE(root_iocg->level > 0);
+
+ list_for_each_entry(iocg, &inner_walk, walk_list) {
+ iocg->child_adjusted_sum = 0;
+ iocg->hweight_donating = 0;
+ iocg->hweight_after_donation = 0;
+ }
+
+ /*
+ * Propagate the donating budget (b_t) and after donation budget (b'_t)
+ * up the hierarchy.
+ */
+ list_for_each_entry(iocg, surpluses, surplus_list) {
+ struct ioc_gq *parent = iocg->ancestors[iocg->level - 1];
+
+ parent->hweight_donating += iocg->hweight_donating;
+ parent->hweight_after_donation += iocg->hweight_after_donation;
+ }
+
+ list_for_each_entry_reverse(iocg, &inner_walk, walk_list) {
+ if (iocg->level > 0) {
+ struct ioc_gq *parent = iocg->ancestors[iocg->level - 1];
+
+ parent->hweight_donating += iocg->hweight_donating;
+ parent->hweight_after_donation += iocg->hweight_after_donation;
+ }
+ }
+
+ /*
+ * Calculate inner hwa's (b) and make sure the donation values are
+ * within the accepted ranges as we're doing low res calculations with
+ * roundups.
+ */
+ list_for_each_entry(iocg, &inner_walk, walk_list) {
+ if (iocg->level) {
+ struct ioc_gq *parent = iocg->ancestors[iocg->level - 1];
+
+ iocg->hweight_active = DIV64_U64_ROUND_UP(
+ (u64)parent->hweight_active * iocg->active,
+ parent->child_active_sum);
+
+ }
+
+ iocg->hweight_donating = min(iocg->hweight_donating,
+ iocg->hweight_active);
+ iocg->hweight_after_donation = min(iocg->hweight_after_donation,
+ iocg->hweight_donating - 1);
+ if (WARN_ON_ONCE(iocg->hweight_active <= 1 ||
+ iocg->hweight_donating <= 1 ||
+ iocg->hweight_after_donation == 0)) {
+ pr_warn("iocg: invalid donation weights in ");
+ pr_cont_cgroup_path(iocg_to_blkg(iocg)->blkcg->css.cgroup);
+ pr_cont(": active=%u donating=%u after=%u\n",
+ iocg->hweight_active, iocg->hweight_donating,
+ iocg->hweight_after_donation);
+ }
+ }
+
+ /*
+ * Calculate the global donation rate (gamma) - the rate to adjust
+ * non-donating budgets by.
+ *
+ * No need to use 64bit multiplication here as the first operand is
+ * guaranteed to be smaller than WEIGHT_ONE (1<<16).
+ *
+ * We know that there are beneficiary nodes and the sum of the donating
+ * hweights can't be whole; however, due to the round-ups during hweight
+ * calculations, root_iocg->hweight_donating might still end up equal to
+ * or greater than whole. Limit the range when calculating the divider.
+ *
+ * gamma = (1 - t_r') / (1 - t_r)
+ */
+ gamma = DIV_ROUND_UP(
+ (WEIGHT_ONE - root_iocg->hweight_after_donation) * WEIGHT_ONE,
+ WEIGHT_ONE - min_t(u32, root_iocg->hweight_donating, WEIGHT_ONE - 1));
+
+ /*
+ * Calculate adjusted hwi, child_adjusted_sum and inuse for the inner
+ * nodes.
+ */
+ list_for_each_entry(iocg, &inner_walk, walk_list) {
+ struct ioc_gq *parent;
+ u32 inuse, wpt, wptp;
+ u64 st, sf;
+
+ if (iocg->level == 0) {
+ /* adjusted weight sum for 1st level: s' = s * b_pf / b'_pf */
+ iocg->child_adjusted_sum = DIV64_U64_ROUND_UP(
+ iocg->child_active_sum * (WEIGHT_ONE - iocg->hweight_donating),
+ WEIGHT_ONE - iocg->hweight_after_donation);
+ continue;
+ }
+
+ parent = iocg->ancestors[iocg->level - 1];
+
+ /* b' = gamma * b_f + b_t' */
+ iocg->hweight_inuse = DIV64_U64_ROUND_UP(
+ (u64)gamma * (iocg->hweight_active - iocg->hweight_donating),
+ WEIGHT_ONE) + iocg->hweight_after_donation;
+
+ /* w' = s' * b' / b'_p */
+ inuse = DIV64_U64_ROUND_UP(
+ (u64)parent->child_adjusted_sum * iocg->hweight_inuse,
+ parent->hweight_inuse);
+
+ /* adjusted weight sum for children: s' = s_f + s_t * w'_pt / w_pt */
+ st = DIV64_U64_ROUND_UP(
+ iocg->child_active_sum * iocg->hweight_donating,
+ iocg->hweight_active);
+ sf = iocg->child_active_sum - st;
+ wpt = DIV64_U64_ROUND_UP(
+ (u64)iocg->active * iocg->hweight_donating,
+ iocg->hweight_active);
+ wptp = DIV64_U64_ROUND_UP(
+ (u64)inuse * iocg->hweight_after_donation,
+ iocg->hweight_inuse);
+
+ iocg->child_adjusted_sum = sf + DIV64_U64_ROUND_UP(st * wptp, wpt);
+ }
+
+ /*
+ * All inner nodes now have ->hweight_inuse and ->child_adjusted_sum and
+ * we can finally determine leaf adjustments.
+ */
+ list_for_each_entry(iocg, surpluses, surplus_list) {
+ struct ioc_gq *parent = iocg->ancestors[iocg->level - 1];
+ u32 inuse;
+
+ /*
+ * In-debt iocgs participated in the donation calculation with
+ * the minimum target hweight_inuse. Configuring inuse
+ * accordingly would work fine but debt handling expects
+ * @iocg->inuse stay at the minimum and we don't wanna
+ * interfere.
+ */
+ if (iocg->abs_vdebt) {
+ WARN_ON_ONCE(iocg->inuse > 1);
+ continue;
+ }
+
+ /* w' = s' * b' / b'_p, note that b' == b'_t for donating leaves */
+ inuse = DIV64_U64_ROUND_UP(
+ parent->child_adjusted_sum * iocg->hweight_after_donation,
+ parent->hweight_inuse);
+
+ TRACE_IOCG_PATH(inuse_transfer, iocg, now,
+ iocg->inuse, inuse,
+ iocg->hweight_inuse,
+ iocg->hweight_after_donation);
+
+ __propagate_weights(iocg, iocg->active, inuse, true, now);
+ }
+
+ /* walk list should be dissolved after use */
+ list_for_each_entry_safe(iocg, tiocg, &inner_walk, walk_list)
+ list_del_init(&iocg->walk_list);
+}
+
+/*
+ * A low weight iocg can amass a large amount of debt, for example, when
+ * anonymous memory gets reclaimed aggressively. If the system has a lot of
+ * memory paired with a slow IO device, the debt can span multiple seconds or
+ * more. If there are no other subsequent IO issuers, the in-debt iocg may end
+ * up blocked paying its debt while the IO device is idle.
+ *
+ * The following protects against such cases. If the device has been
+ * sufficiently idle for a while, the debts are halved and delays are
+ * recalculated.
+ */
+static void ioc_forgive_debts(struct ioc *ioc, u64 usage_us_sum, int nr_debtors,
+ struct ioc_now *now)
+{
+ struct ioc_gq *iocg;
+ u64 dur, usage_pct, nr_cycles;
+
+ /* if no debtor, reset the cycle */
+ if (!nr_debtors) {
+ ioc->dfgv_period_at = now->now;
+ ioc->dfgv_period_rem = 0;
+ ioc->dfgv_usage_us_sum = 0;
+ return;
+ }
+
+ /*
+ * Debtors can pass through a lot of writes choking the device and we
+ * don't want to be forgiving debts while the device is struggling from
+ * write bursts. If we're missing latency targets, consider the device
+ * fully utilized.
+ */
+ if (ioc->busy_level > 0)
+ usage_us_sum = max_t(u64, usage_us_sum, ioc->period_us);
+
+ ioc->dfgv_usage_us_sum += usage_us_sum;
+ if (time_before64(now->now, ioc->dfgv_period_at + DFGV_PERIOD))
+ return;
+
+ /*
+ * At least DFGV_PERIOD has passed since the last period. Calculate the
+ * average usage and reset the period counters.
+ */
+ dur = now->now - ioc->dfgv_period_at;
+ usage_pct = div64_u64(100 * ioc->dfgv_usage_us_sum, dur);
+
+ ioc->dfgv_period_at = now->now;
+ ioc->dfgv_usage_us_sum = 0;
+
+ /* if was too busy, reset everything */
+ if (usage_pct > DFGV_USAGE_PCT) {
+ ioc->dfgv_period_rem = 0;
+ return;
+ }
+
+ /*
+ * Usage is lower than threshold. Let's forgive some debts. Debt
+ * forgiveness runs off of the usual ioc timer but its period usually
+ * doesn't match ioc's. Compensate the difference by performing the
+ * reduction as many times as would fit in the duration since the last
+ * run and carrying over the left-over duration in @ioc->dfgv_period_rem
+ * - if ioc period is 75% of DFGV_PERIOD, one out of three consecutive
+ * reductions is doubled.
+ */
+ nr_cycles = dur + ioc->dfgv_period_rem;
+ ioc->dfgv_period_rem = do_div(nr_cycles, DFGV_PERIOD);
+
+ list_for_each_entry(iocg, &ioc->active_iocgs, active_list) {
+ u64 __maybe_unused old_debt, __maybe_unused old_delay;
+
+ if (!iocg->abs_vdebt && !iocg->delay)
+ continue;
+
+ spin_lock(&iocg->waitq.lock);
+
+ old_debt = iocg->abs_vdebt;
+ old_delay = iocg->delay;
+
+ if (iocg->abs_vdebt)
+ iocg->abs_vdebt = iocg->abs_vdebt >> nr_cycles ?: 1;
+ if (iocg->delay)
+ iocg->delay = iocg->delay >> nr_cycles ?: 1;
+
+ iocg_kick_waitq(iocg, true, now);
+
+ TRACE_IOCG_PATH(iocg_forgive_debt, iocg, now, usage_pct,
+ old_debt, iocg->abs_vdebt,
+ old_delay, iocg->delay);
+
+ spin_unlock(&iocg->waitq.lock);
+ }
+}
+
+static void ioc_timer_fn(struct timer_list *timer)
+{
+ struct ioc *ioc = container_of(timer, struct ioc, timer);
+ struct ioc_gq *iocg, *tiocg;
+ struct ioc_now now;
+ LIST_HEAD(surpluses);
+ int nr_debtors = 0, nr_shortages = 0, nr_lagging = 0;
+ u64 usage_us_sum = 0;
+ u32 ppm_rthr = MILLION - ioc->params.qos[QOS_RPPM];
+ u32 ppm_wthr = MILLION - ioc->params.qos[QOS_WPPM];
+ u32 missed_ppm[2], rq_wait_pct;
+ u64 period_vtime;
+ int prev_busy_level;
+
+ /* how were the latencies during the period? */
+ ioc_lat_stat(ioc, missed_ppm, &rq_wait_pct);
+
+ /* take care of active iocgs */
+ spin_lock_irq(&ioc->lock);
+
+ ioc_now(ioc, &now);
+
+ period_vtime = now.vnow - ioc->period_at_vtime;
+ if (WARN_ON_ONCE(!period_vtime)) {
+ spin_unlock_irq(&ioc->lock);
+ return;
+ }
+
+ /*
+ * Waiters determine the sleep durations based on the vrate they
+ * saw at the time of sleep. If vrate has increased, some waiters
+ * could be sleeping for too long. Wake up tardy waiters which
+ * should have woken up in the last period and expire idle iocgs.
+ */
+ list_for_each_entry_safe(iocg, tiocg, &ioc->active_iocgs, active_list) {
+ if (!waitqueue_active(&iocg->waitq) && !iocg->abs_vdebt &&
+ !iocg->delay && !iocg_is_idle(iocg))
+ continue;
+
+ spin_lock(&iocg->waitq.lock);
+
+ /* flush wait and indebt stat deltas */
+ if (iocg->wait_since) {
+ iocg->local_stat.wait_us += now.now - iocg->wait_since;
+ iocg->wait_since = now.now;
+ }
+ if (iocg->indebt_since) {
+ iocg->local_stat.indebt_us +=
+ now.now - iocg->indebt_since;
+ iocg->indebt_since = now.now;
+ }
+ if (iocg->indelay_since) {
+ iocg->local_stat.indelay_us +=
+ now.now - iocg->indelay_since;
+ iocg->indelay_since = now.now;
+ }
+
+ if (waitqueue_active(&iocg->waitq) || iocg->abs_vdebt ||
+ iocg->delay) {
+ /* might be oversleeping vtime / hweight changes, kick */
+ iocg_kick_waitq(iocg, true, &now);
+ if (iocg->abs_vdebt || iocg->delay)
+ nr_debtors++;
+ } else if (iocg_is_idle(iocg)) {
+ /* no waiter and idle, deactivate */
+ u64 vtime = atomic64_read(&iocg->vtime);
+ s64 excess;
+
+ /*
+ * @iocg has been inactive for a full duration and will
+ * have a high budget. Account anything above target as
+ * error and throw away. On reactivation, it'll start
+ * with the target budget.
+ */
+ excess = now.vnow - vtime - ioc->margins.target;
+ if (excess > 0) {
+ u32 old_hwi;
+
+ current_hweight(iocg, NULL, &old_hwi);
+ ioc->vtime_err -= div64_u64(excess * old_hwi,
+ WEIGHT_ONE);
+ }
+
+ __propagate_weights(iocg, 0, 0, false, &now);
+ list_del_init(&iocg->active_list);
+ }
+
+ spin_unlock(&iocg->waitq.lock);
+ }
+ commit_weights(ioc);
+
+ /*
+ * Wait and indebt stat are flushed above and the donation calculation
+ * below needs updated usage stat. Let's bring stat up-to-date.
+ */
+ iocg_flush_stat(&ioc->active_iocgs, &now);
+
+ /* calc usage and see whether some weights need to be moved around */
+ list_for_each_entry(iocg, &ioc->active_iocgs, active_list) {
+ u64 vdone, vtime, usage_us, usage_dur;
+ u32 usage, hw_active, hw_inuse;
+
+ /*
+ * Collect unused and wind vtime closer to vnow to prevent
+ * iocgs from accumulating a large amount of budget.
+ */
+ vdone = atomic64_read(&iocg->done_vtime);
+ vtime = atomic64_read(&iocg->vtime);
+ current_hweight(iocg, &hw_active, &hw_inuse);
+
+ /*
+ * Latency QoS detection doesn't account for IOs which are
+ * in-flight for longer than a period. Detect them by
+ * comparing vdone against period start. If lagging behind
+ * IOs from past periods, don't increase vrate.
+ */
+ if ((ppm_rthr != MILLION || ppm_wthr != MILLION) &&
+ !atomic_read(&iocg_to_blkg(iocg)->use_delay) &&
+ time_after64(vtime, vdone) &&
+ time_after64(vtime, now.vnow -
+ MAX_LAGGING_PERIODS * period_vtime) &&
+ time_before64(vdone, now.vnow - period_vtime))
+ nr_lagging++;
+
+ /*
+ * Determine absolute usage factoring in in-flight IOs to avoid
+ * high-latency completions appearing as idle.
+ */
+ usage_us = iocg->usage_delta_us;
+ usage_us_sum += usage_us;
+
+ if (vdone != vtime) {
+ u64 inflight_us = DIV64_U64_ROUND_UP(
+ cost_to_abs_cost(vtime - vdone, hw_inuse),
+ ioc->vtime_base_rate);
+ usage_us = max(usage_us, inflight_us);
+ }
+
+ /* convert to hweight based usage ratio */
+ if (time_after64(iocg->activated_at, ioc->period_at))
+ usage_dur = max_t(u64, now.now - iocg->activated_at, 1);
+ else
+ usage_dur = max_t(u64, now.now - ioc->period_at, 1);
+
+ usage = clamp_t(u32,
+ DIV64_U64_ROUND_UP(usage_us * WEIGHT_ONE,
+ usage_dur),
+ 1, WEIGHT_ONE);
+
+ /* see whether there's surplus vtime */
+ WARN_ON_ONCE(!list_empty(&iocg->surplus_list));
+ if (hw_inuse < hw_active ||
+ (!waitqueue_active(&iocg->waitq) &&
+ time_before64(vtime, now.vnow - ioc->margins.low))) {
+ u32 hwa, old_hwi, hwm, new_hwi;
+
+ /*
+ * Already donating or accumulated enough to start.
+ * Determine the donation amount.
+ */
+ current_hweight(iocg, &hwa, &old_hwi);
+ hwm = current_hweight_max(iocg);
+ new_hwi = hweight_after_donation(iocg, old_hwi, hwm,
+ usage, &now);
+ /*
+ * Donation calculation assumes hweight_after_donation
+ * to be positive, a condition that a donor w/ hwa < 2
+ * can't meet. Don't bother with donation if hwa is
+ * below 2. It's not gonna make a meaningful difference
+ * anyway.
+ */
+ if (new_hwi < hwm && hwa >= 2) {
+ iocg->hweight_donating = hwa;
+ iocg->hweight_after_donation = new_hwi;
+ list_add(&iocg->surplus_list, &surpluses);
+ } else if (!iocg->abs_vdebt) {
+ /*
+ * @iocg doesn't have enough to donate. Reset
+ * its inuse to active.
+ *
+ * Don't reset debtors as their inuse's are
+ * owned by debt handling. This shouldn't affect
+ * donation calculuation in any meaningful way
+ * as @iocg doesn't have a meaningful amount of
+ * share anyway.
+ */
+ TRACE_IOCG_PATH(inuse_shortage, iocg, &now,
+ iocg->inuse, iocg->active,
+ iocg->hweight_inuse, new_hwi);
+
+ __propagate_weights(iocg, iocg->active,
+ iocg->active, true, &now);
+ nr_shortages++;
+ }
+ } else {
+ /* genuinely short on vtime */
+ nr_shortages++;
+ }
+ }
+
+ if (!list_empty(&surpluses) && nr_shortages)
+ transfer_surpluses(&surpluses, &now);
+
+ commit_weights(ioc);
+
+ /* surplus list should be dissolved after use */
+ list_for_each_entry_safe(iocg, tiocg, &surpluses, surplus_list)
+ list_del_init(&iocg->surplus_list);
+
+ /*
+ * If q is getting clogged or we're missing too much, we're issuing
+ * too much IO and should lower vtime rate. If we're not missing
+ * and experiencing shortages but not surpluses, we're too stingy
+ * and should increase vtime rate.
+ */
+ prev_busy_level = ioc->busy_level;
+ if (rq_wait_pct > RQ_WAIT_BUSY_PCT ||
+ missed_ppm[READ] > ppm_rthr ||
+ missed_ppm[WRITE] > ppm_wthr) {
+ /* clearly missing QoS targets, slow down vrate */
+ ioc->busy_level = max(ioc->busy_level, 0);
+ ioc->busy_level++;
+ } else if (rq_wait_pct <= RQ_WAIT_BUSY_PCT * UNBUSY_THR_PCT / 100 &&
+ missed_ppm[READ] <= ppm_rthr * UNBUSY_THR_PCT / 100 &&
+ missed_ppm[WRITE] <= ppm_wthr * UNBUSY_THR_PCT / 100) {
+ /* QoS targets are being met with >25% margin */
+ if (nr_shortages) {
+ /*
+ * We're throttling while the device has spare
+ * capacity. If vrate was being slowed down, stop.
+ */
+ ioc->busy_level = min(ioc->busy_level, 0);
+
+ /*
+ * If there are IOs spanning multiple periods, wait
+ * them out before pushing the device harder.
+ */
+ if (!nr_lagging)
+ ioc->busy_level--;
+ } else {
+ /*
+ * Nobody is being throttled and the users aren't
+ * issuing enough IOs to saturate the device. We
+ * simply don't know how close the device is to
+ * saturation. Coast.
+ */
+ ioc->busy_level = 0;
+ }
+ } else {
+ /* inside the hysterisis margin, we're good */
+ ioc->busy_level = 0;
+ }
+
+ ioc->busy_level = clamp(ioc->busy_level, -1000, 1000);
+
+ if (ioc->busy_level > 0 || (ioc->busy_level < 0 && !nr_lagging)) {
+ u64 vrate = ioc->vtime_base_rate;
+ u64 vrate_min = ioc->vrate_min, vrate_max = ioc->vrate_max;
+
+ /* rq_wait signal is always reliable, ignore user vrate_min */
+ if (rq_wait_pct > RQ_WAIT_BUSY_PCT)
+ vrate_min = VRATE_MIN;
+
+ /*
+ * If vrate is out of bounds, apply clamp gradually as the
+ * bounds can change abruptly. Otherwise, apply busy_level
+ * based adjustment.
+ */
+ if (vrate < vrate_min) {
+ vrate = div64_u64(vrate * (100 + VRATE_CLAMP_ADJ_PCT),
+ 100);
+ vrate = min(vrate, vrate_min);
+ } else if (vrate > vrate_max) {
+ vrate = div64_u64(vrate * (100 - VRATE_CLAMP_ADJ_PCT),
+ 100);
+ vrate = max(vrate, vrate_max);
+ } else {
+ int idx = min_t(int, abs(ioc->busy_level),
+ ARRAY_SIZE(vrate_adj_pct) - 1);
+ u32 adj_pct = vrate_adj_pct[idx];
+
+ if (ioc->busy_level > 0)
+ adj_pct = 100 - adj_pct;
+ else
+ adj_pct = 100 + adj_pct;
+
+ vrate = clamp(DIV64_U64_ROUND_UP(vrate * adj_pct, 100),
+ vrate_min, vrate_max);
+ }
+
+ trace_iocost_ioc_vrate_adj(ioc, vrate, missed_ppm, rq_wait_pct,
+ nr_lagging, nr_shortages);
+
+ ioc->vtime_base_rate = vrate;
+ ioc_refresh_margins(ioc);
+ } else if (ioc->busy_level != prev_busy_level || nr_lagging) {
+ trace_iocost_ioc_vrate_adj(ioc, atomic64_read(&ioc->vtime_rate),
+ missed_ppm, rq_wait_pct, nr_lagging,
+ nr_shortages);
+ }
+
+ ioc_refresh_params(ioc, false);
+
+ ioc_forgive_debts(ioc, usage_us_sum, nr_debtors, &now);
+
+ /*
+ * This period is done. Move onto the next one. If nothing's
+ * going on with the device, stop the timer.
+ */
+ atomic64_inc(&ioc->cur_period);
+
+ if (ioc->running != IOC_STOP) {
+ if (!list_empty(&ioc->active_iocgs)) {
+ ioc_start_period(ioc, &now);
+ } else {
+ ioc->busy_level = 0;
+ ioc->vtime_err = 0;
+ ioc->running = IOC_IDLE;
+ }
+
+ ioc_refresh_vrate(ioc, &now);
+ }
+
+ spin_unlock_irq(&ioc->lock);
+}
+
+static u64 adjust_inuse_and_calc_cost(struct ioc_gq *iocg, u64 vtime,
+ u64 abs_cost, struct ioc_now *now)
+{
+ struct ioc *ioc = iocg->ioc;
+ struct ioc_margins *margins = &ioc->margins;
+ u32 __maybe_unused old_inuse = iocg->inuse, __maybe_unused old_hwi;
+ u32 hwi, adj_step;
+ s64 margin;
+ u64 cost, new_inuse;
+ unsigned long flags;
+
+ current_hweight(iocg, NULL, &hwi);
+ old_hwi = hwi;
+ cost = abs_cost_to_cost(abs_cost, hwi);
+ margin = now->vnow - vtime - cost;
+
+ /* debt handling owns inuse for debtors */
+ if (iocg->abs_vdebt)
+ return cost;
+
+ /*
+ * We only increase inuse during period and do so iff the margin has
+ * deteriorated since the previous adjustment.
+ */
+ if (margin >= iocg->saved_margin || margin >= margins->low ||
+ iocg->inuse == iocg->active)
+ return cost;
+
+ spin_lock_irqsave(&ioc->lock, flags);
+
+ /* we own inuse only when @iocg is in the normal active state */
+ if (iocg->abs_vdebt || list_empty(&iocg->active_list)) {
+ spin_unlock_irqrestore(&ioc->lock, flags);
+ return cost;
+ }
+
+ /*
+ * Bump up inuse till @abs_cost fits in the existing budget.
+ * adj_step must be determined after acquiring ioc->lock - we might
+ * have raced and lost to another thread for activation and could
+ * be reading 0 iocg->active before ioc->lock which will lead to
+ * infinite loop.
+ */
+ new_inuse = iocg->inuse;
+ adj_step = DIV_ROUND_UP(iocg->active * INUSE_ADJ_STEP_PCT, 100);
+ do {
+ new_inuse = new_inuse + adj_step;
+ propagate_weights(iocg, iocg->active, new_inuse, true, now);
+ current_hweight(iocg, NULL, &hwi);
+ cost = abs_cost_to_cost(abs_cost, hwi);
+ } while (time_after64(vtime + cost, now->vnow) &&
+ iocg->inuse != iocg->active);
+
+ spin_unlock_irqrestore(&ioc->lock, flags);
+
+ TRACE_IOCG_PATH(inuse_adjust, iocg, now,
+ old_inuse, iocg->inuse, old_hwi, hwi);
+
+ return cost;
+}
+
+static void calc_vtime_cost_builtin(struct bio *bio, struct ioc_gq *iocg,
+ bool is_merge, u64 *costp)
+{
+ struct ioc *ioc = iocg->ioc;
+ u64 coef_seqio, coef_randio, coef_page;
+ u64 pages = max_t(u64, bio_sectors(bio) >> IOC_SECT_TO_PAGE_SHIFT, 1);
+ u64 seek_pages = 0;
+ u64 cost = 0;
+
+ switch (bio_op(bio)) {
+ case REQ_OP_READ:
+ coef_seqio = ioc->params.lcoefs[LCOEF_RSEQIO];
+ coef_randio = ioc->params.lcoefs[LCOEF_RRANDIO];
+ coef_page = ioc->params.lcoefs[LCOEF_RPAGE];
+ break;
+ case REQ_OP_WRITE:
+ coef_seqio = ioc->params.lcoefs[LCOEF_WSEQIO];
+ coef_randio = ioc->params.lcoefs[LCOEF_WRANDIO];
+ coef_page = ioc->params.lcoefs[LCOEF_WPAGE];
+ break;
+ default:
+ goto out;
+ }
+
+ if (iocg->cursor) {
+ seek_pages = abs(bio->bi_iter.bi_sector - iocg->cursor);
+ seek_pages >>= IOC_SECT_TO_PAGE_SHIFT;
+ }
+
+ if (!is_merge) {
+ if (seek_pages > LCOEF_RANDIO_PAGES) {
+ cost += coef_randio;
+ } else {
+ cost += coef_seqio;
+ }
+ }
+ cost += pages * coef_page;
+out:
+ *costp = cost;
+}
+
+static u64 calc_vtime_cost(struct bio *bio, struct ioc_gq *iocg, bool is_merge)
+{
+ u64 cost;
+
+ calc_vtime_cost_builtin(bio, iocg, is_merge, &cost);
+ return cost;
+}
+
+static void calc_size_vtime_cost_builtin(struct request *rq, struct ioc *ioc,
+ u64 *costp)
+{
+ unsigned int pages = blk_rq_stats_sectors(rq) >> IOC_SECT_TO_PAGE_SHIFT;
+
+ switch (req_op(rq)) {
+ case REQ_OP_READ:
+ *costp = pages * ioc->params.lcoefs[LCOEF_RPAGE];
+ break;
+ case REQ_OP_WRITE:
+ *costp = pages * ioc->params.lcoefs[LCOEF_WPAGE];
+ break;
+ default:
+ *costp = 0;
+ }
+}
+
+static u64 calc_size_vtime_cost(struct request *rq, struct ioc *ioc)
+{
+ u64 cost;
+
+ calc_size_vtime_cost_builtin(rq, ioc, &cost);
+ return cost;
+}
+
+static void ioc_rqos_throttle(struct rq_qos *rqos, struct bio *bio)
+{
+ struct blkcg_gq *blkg = bio->bi_blkg;
+ struct ioc *ioc = rqos_to_ioc(rqos);
+ struct ioc_gq *iocg = blkg_to_iocg(blkg);
+ struct ioc_now now;
+ struct iocg_wait wait;
+ u64 abs_cost, cost, vtime;
+ bool use_debt, ioc_locked;
+ unsigned long flags;
+
+ /* bypass IOs if disabled, still initializing, or for root cgroup */
+ if (!ioc->enabled || !iocg || !iocg->level)
+ return;
+
+ /* calculate the absolute vtime cost */
+ abs_cost = calc_vtime_cost(bio, iocg, false);
+ if (!abs_cost)
+ return;
+
+ if (!iocg_activate(iocg, &now))
+ return;
+
+ iocg->cursor = bio_end_sector(bio);
+ vtime = atomic64_read(&iocg->vtime);
+ cost = adjust_inuse_and_calc_cost(iocg, vtime, abs_cost, &now);
+
+ /*
+ * If no one's waiting and within budget, issue right away. The
+ * tests are racy but the races aren't systemic - we only miss once
+ * in a while which is fine.
+ */
+ if (!waitqueue_active(&iocg->waitq) && !iocg->abs_vdebt &&
+ time_before_eq64(vtime + cost, now.vnow)) {
+ iocg_commit_bio(iocg, bio, abs_cost, cost);
+ return;
+ }
+
+ /*
+ * We're over budget. This can be handled in two ways. IOs which may
+ * cause priority inversions are punted to @ioc->aux_iocg and charged as
+ * debt. Otherwise, the issuer is blocked on @iocg->waitq. Debt handling
+ * requires @ioc->lock, waitq handling @iocg->waitq.lock. Determine
+ * whether debt handling is needed and acquire locks accordingly.
+ */
+ use_debt = bio_issue_as_root_blkg(bio) || fatal_signal_pending(current);
+ ioc_locked = use_debt || READ_ONCE(iocg->abs_vdebt);
+retry_lock:
+ iocg_lock(iocg, ioc_locked, &flags);
+
+ /*
+ * @iocg must stay activated for debt and waitq handling. Deactivation
+ * is synchronized against both ioc->lock and waitq.lock and we won't
+ * get deactivated as long as we're waiting or has debt, so we're good
+ * if we're activated here. In the unlikely cases that we aren't, just
+ * issue the IO.
+ */
+ if (unlikely(list_empty(&iocg->active_list))) {
+ iocg_unlock(iocg, ioc_locked, &flags);
+ iocg_commit_bio(iocg, bio, abs_cost, cost);
+ return;
+ }
+
+ /*
+ * We're over budget. If @bio has to be issued regardless, remember
+ * the abs_cost instead of advancing vtime. iocg_kick_waitq() will pay
+ * off the debt before waking more IOs.
+ *
+ * This way, the debt is continuously paid off each period with the
+ * actual budget available to the cgroup. If we just wound vtime, we
+ * would incorrectly use the current hw_inuse for the entire amount
+ * which, for example, can lead to the cgroup staying blocked for a
+ * long time even with substantially raised hw_inuse.
+ *
+ * An iocg with vdebt should stay online so that the timer can keep
+ * deducting its vdebt and [de]activate use_delay mechanism
+ * accordingly. We don't want to race against the timer trying to
+ * clear them and leave @iocg inactive w/ dangling use_delay heavily
+ * penalizing the cgroup and its descendants.
+ */
+ if (use_debt) {
+ iocg_incur_debt(iocg, abs_cost, &now);
+ if (iocg_kick_delay(iocg, &now))
+ blkcg_schedule_throttle(rqos->q,
+ (bio->bi_opf & REQ_SWAP) == REQ_SWAP);
+ iocg_unlock(iocg, ioc_locked, &flags);
+ return;
+ }
+
+ /* guarantee that iocgs w/ waiters have maximum inuse */
+ if (!iocg->abs_vdebt && iocg->inuse != iocg->active) {
+ if (!ioc_locked) {
+ iocg_unlock(iocg, false, &flags);
+ ioc_locked = true;
+ goto retry_lock;
+ }
+ propagate_weights(iocg, iocg->active, iocg->active, true,
+ &now);
+ }
+
+ /*
+ * Append self to the waitq and schedule the wakeup timer if we're
+ * the first waiter. The timer duration is calculated based on the
+ * current vrate. vtime and hweight changes can make it too short
+ * or too long. Each wait entry records the absolute cost it's
+ * waiting for to allow re-evaluation using a custom wait entry.
+ *
+ * If too short, the timer simply reschedules itself. If too long,
+ * the period timer will notice and trigger wakeups.
+ *
+ * All waiters are on iocg->waitq and the wait states are
+ * synchronized using waitq.lock.
+ */
+ init_waitqueue_func_entry(&wait.wait, iocg_wake_fn);
+ wait.wait.private = current;
+ wait.bio = bio;
+ wait.abs_cost = abs_cost;
+ wait.committed = false; /* will be set true by waker */
+
+ __add_wait_queue_entry_tail(&iocg->waitq, &wait.wait);
+ iocg_kick_waitq(iocg, ioc_locked, &now);
+
+ iocg_unlock(iocg, ioc_locked, &flags);
+
+ while (true) {
+ set_current_state(TASK_UNINTERRUPTIBLE);
+ if (wait.committed)
+ break;
+ io_schedule();
+ }
+
+ /* waker already committed us, proceed */
+ finish_wait(&iocg->waitq, &wait.wait);
+}
+
+static void ioc_rqos_merge(struct rq_qos *rqos, struct request *rq,
+ struct bio *bio)
+{
+ struct ioc_gq *iocg = blkg_to_iocg(bio->bi_blkg);
+ struct ioc *ioc = rqos_to_ioc(rqos);
+ sector_t bio_end = bio_end_sector(bio);
+ struct ioc_now now;
+ u64 vtime, abs_cost, cost;
+ unsigned long flags;
+
+ /* bypass if disabled, still initializing, or for root cgroup */
+ if (!ioc->enabled || !iocg || !iocg->level)
+ return;
+
+ abs_cost = calc_vtime_cost(bio, iocg, true);
+ if (!abs_cost)
+ return;
+
+ ioc_now(ioc, &now);
+
+ vtime = atomic64_read(&iocg->vtime);
+ cost = adjust_inuse_and_calc_cost(iocg, vtime, abs_cost, &now);
+
+ /* update cursor if backmerging into the request at the cursor */
+ if (blk_rq_pos(rq) < bio_end &&
+ blk_rq_pos(rq) + blk_rq_sectors(rq) == iocg->cursor)
+ iocg->cursor = bio_end;
+
+ /*
+ * Charge if there's enough vtime budget and the existing request has
+ * cost assigned.
+ */
+ if (rq->bio && rq->bio->bi_iocost_cost &&
+ time_before_eq64(atomic64_read(&iocg->vtime) + cost, now.vnow)) {
+ iocg_commit_bio(iocg, bio, abs_cost, cost);
+ return;
+ }
+
+ /*
+ * Otherwise, account it as debt if @iocg is online, which it should
+ * be for the vast majority of cases. See debt handling in
+ * ioc_rqos_throttle() for details.
+ */
+ spin_lock_irqsave(&ioc->lock, flags);
+ spin_lock(&iocg->waitq.lock);
+
+ if (likely(!list_empty(&iocg->active_list))) {
+ iocg_incur_debt(iocg, abs_cost, &now);
+ if (iocg_kick_delay(iocg, &now))
+ blkcg_schedule_throttle(rqos->q,
+ (bio->bi_opf & REQ_SWAP) == REQ_SWAP);
+ } else {
+ iocg_commit_bio(iocg, bio, abs_cost, cost);
+ }
+
+ spin_unlock(&iocg->waitq.lock);
+ spin_unlock_irqrestore(&ioc->lock, flags);
+}
+
+static void ioc_rqos_done_bio(struct rq_qos *rqos, struct bio *bio)
+{
+ struct ioc_gq *iocg = blkg_to_iocg(bio->bi_blkg);
+
+ if (iocg && bio->bi_iocost_cost)
+ atomic64_add(bio->bi_iocost_cost, &iocg->done_vtime);
+}
+
+static void ioc_rqos_done(struct rq_qos *rqos, struct request *rq)
+{
+ struct ioc *ioc = rqos_to_ioc(rqos);
+ struct ioc_pcpu_stat *ccs;
+ u64 on_q_ns, rq_wait_ns, size_nsec;
+ int pidx, rw;
+
+ if (!ioc->enabled || !rq->alloc_time_ns || !rq->start_time_ns)
+ return;
+
+ switch (req_op(rq) & REQ_OP_MASK) {
+ case REQ_OP_READ:
+ pidx = QOS_RLAT;
+ rw = READ;
+ break;
+ case REQ_OP_WRITE:
+ pidx = QOS_WLAT;
+ rw = WRITE;
+ break;
+ default:
+ return;
+ }
+
+ on_q_ns = ktime_get_ns() - rq->alloc_time_ns;
+ rq_wait_ns = rq->start_time_ns - rq->alloc_time_ns;
+ size_nsec = div64_u64(calc_size_vtime_cost(rq, ioc), VTIME_PER_NSEC);
+
+ ccs = get_cpu_ptr(ioc->pcpu_stat);
+
+ if (on_q_ns <= size_nsec ||
+ on_q_ns - size_nsec <= ioc->params.qos[pidx] * NSEC_PER_USEC)
+ local_inc(&ccs->missed[rw].nr_met);
+ else
+ local_inc(&ccs->missed[rw].nr_missed);
+
+ local64_add(rq_wait_ns, &ccs->rq_wait_ns);
+
+ put_cpu_ptr(ccs);
+}
+
+static void ioc_rqos_queue_depth_changed(struct rq_qos *rqos)
+{
+ struct ioc *ioc = rqos_to_ioc(rqos);
+
+ spin_lock_irq(&ioc->lock);
+ ioc_refresh_params(ioc, false);
+ spin_unlock_irq(&ioc->lock);
+}
+
+static void ioc_rqos_exit(struct rq_qos *rqos)
+{
+ struct ioc *ioc = rqos_to_ioc(rqos);
+
+ blkcg_deactivate_policy(rqos->q, &blkcg_policy_iocost);
+
+ spin_lock_irq(&ioc->lock);
+ ioc->running = IOC_STOP;
+ spin_unlock_irq(&ioc->lock);
+
+ del_timer_sync(&ioc->timer);
+ free_percpu(ioc->pcpu_stat);
+ kfree(ioc);
+}
+
+static struct rq_qos_ops ioc_rqos_ops = {
+ .throttle = ioc_rqos_throttle,
+ .merge = ioc_rqos_merge,
+ .done_bio = ioc_rqos_done_bio,
+ .done = ioc_rqos_done,
+ .queue_depth_changed = ioc_rqos_queue_depth_changed,
+ .exit = ioc_rqos_exit,
+};
+
+static int blk_iocost_init(struct request_queue *q)
+{
+ struct ioc *ioc;
+ struct rq_qos *rqos;
+ int i, cpu, ret;
+
+ ioc = kzalloc(sizeof(*ioc), GFP_KERNEL);
+ if (!ioc)
+ return -ENOMEM;
+
+ ioc->pcpu_stat = alloc_percpu(struct ioc_pcpu_stat);
+ if (!ioc->pcpu_stat) {
+ kfree(ioc);
+ return -ENOMEM;
+ }
+
+ for_each_possible_cpu(cpu) {
+ struct ioc_pcpu_stat *ccs = per_cpu_ptr(ioc->pcpu_stat, cpu);
+
+ for (i = 0; i < ARRAY_SIZE(ccs->missed); i++) {
+ local_set(&ccs->missed[i].nr_met, 0);
+ local_set(&ccs->missed[i].nr_missed, 0);
+ }
+ local64_set(&ccs->rq_wait_ns, 0);
+ }
+
+ rqos = &ioc->rqos;
+ rqos->id = RQ_QOS_COST;
+ rqos->ops = &ioc_rqos_ops;
+ rqos->q = q;
+
+ spin_lock_init(&ioc->lock);
+ timer_setup(&ioc->timer, ioc_timer_fn, 0);
+ INIT_LIST_HEAD(&ioc->active_iocgs);
+
+ ioc->running = IOC_IDLE;
+ ioc->vtime_base_rate = VTIME_PER_USEC;
+ atomic64_set(&ioc->vtime_rate, VTIME_PER_USEC);
+ seqcount_spinlock_init(&ioc->period_seqcount, &ioc->lock);
+ ioc->period_at = ktime_to_us(ktime_get());
+ atomic64_set(&ioc->cur_period, 0);
+ atomic_set(&ioc->hweight_gen, 0);
+
+ spin_lock_irq(&ioc->lock);
+ ioc->autop_idx = AUTOP_INVALID;
+ ioc_refresh_params(ioc, true);
+ spin_unlock_irq(&ioc->lock);
+
+ /*
+ * rqos must be added before activation to allow iocg_pd_init() to
+ * lookup the ioc from q. This means that the rqos methods may get
+ * called before policy activation completion, can't assume that the
+ * target bio has an iocg associated and need to test for NULL iocg.
+ */
+ rq_qos_add(q, rqos);
+ ret = blkcg_activate_policy(q, &blkcg_policy_iocost);
+ if (ret) {
+ rq_qos_del(q, rqos);
+ free_percpu(ioc->pcpu_stat);
+ kfree(ioc);
+ return ret;
+ }
+ return 0;
+}
+
+static struct blkcg_policy_data *ioc_cpd_alloc(gfp_t gfp)
+{
+ struct ioc_cgrp *iocc;
+
+ iocc = kzalloc(sizeof(struct ioc_cgrp), gfp);
+ if (!iocc)
+ return NULL;
+
+ iocc->dfl_weight = CGROUP_WEIGHT_DFL * WEIGHT_ONE;
+ return &iocc->cpd;
+}
+
+static void ioc_cpd_free(struct blkcg_policy_data *cpd)
+{
+ kfree(container_of(cpd, struct ioc_cgrp, cpd));
+}
+
+static struct blkg_policy_data *ioc_pd_alloc(gfp_t gfp, struct request_queue *q,
+ struct blkcg *blkcg)
+{
+ int levels = blkcg->css.cgroup->level + 1;
+ struct ioc_gq *iocg;
+
+ iocg = kzalloc_node(struct_size(iocg, ancestors, levels), gfp, q->node);
+ if (!iocg)
+ return NULL;
+
+ iocg->pcpu_stat = alloc_percpu_gfp(struct iocg_pcpu_stat, gfp);
+ if (!iocg->pcpu_stat) {
+ kfree(iocg);
+ return NULL;
+ }
+
+ return &iocg->pd;
+}
+
+static void ioc_pd_init(struct blkg_policy_data *pd)
+{
+ struct ioc_gq *iocg = pd_to_iocg(pd);
+ struct blkcg_gq *blkg = pd_to_blkg(&iocg->pd);
+ struct ioc *ioc = q_to_ioc(blkg->q);
+ struct ioc_now now;
+ struct blkcg_gq *tblkg;
+ unsigned long flags;
+
+ ioc_now(ioc, &now);
+
+ iocg->ioc = ioc;
+ atomic64_set(&iocg->vtime, now.vnow);
+ atomic64_set(&iocg->done_vtime, now.vnow);
+ atomic64_set(&iocg->active_period, atomic64_read(&ioc->cur_period));
+ INIT_LIST_HEAD(&iocg->active_list);
+ INIT_LIST_HEAD(&iocg->walk_list);
+ INIT_LIST_HEAD(&iocg->surplus_list);
+ iocg->hweight_active = WEIGHT_ONE;
+ iocg->hweight_inuse = WEIGHT_ONE;
+
+ init_waitqueue_head(&iocg->waitq);
+ hrtimer_init(&iocg->waitq_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
+ iocg->waitq_timer.function = iocg_waitq_timer_fn;
+
+ iocg->level = blkg->blkcg->css.cgroup->level;
+
+ for (tblkg = blkg; tblkg; tblkg = tblkg->parent) {
+ struct ioc_gq *tiocg = blkg_to_iocg(tblkg);
+ iocg->ancestors[tiocg->level] = tiocg;
+ }
+
+ spin_lock_irqsave(&ioc->lock, flags);
+ weight_updated(iocg, &now);
+ spin_unlock_irqrestore(&ioc->lock, flags);
+}
+
+static void ioc_pd_free(struct blkg_policy_data *pd)
+{
+ struct ioc_gq *iocg = pd_to_iocg(pd);
+ struct ioc *ioc = iocg->ioc;
+ unsigned long flags;
+
+ if (ioc) {
+ spin_lock_irqsave(&ioc->lock, flags);
+
+ if (!list_empty(&iocg->active_list)) {
+ struct ioc_now now;
+
+ ioc_now(ioc, &now);
+ propagate_weights(iocg, 0, 0, false, &now);
+ list_del_init(&iocg->active_list);
+ }
+
+ WARN_ON_ONCE(!list_empty(&iocg->walk_list));
+ WARN_ON_ONCE(!list_empty(&iocg->surplus_list));
+
+ spin_unlock_irqrestore(&ioc->lock, flags);
+
+ hrtimer_cancel(&iocg->waitq_timer);
+ }
+ free_percpu(iocg->pcpu_stat);
+ kfree(iocg);
+}
+
+static size_t ioc_pd_stat(struct blkg_policy_data *pd, char *buf, size_t size)
+{
+ struct ioc_gq *iocg = pd_to_iocg(pd);
+ struct ioc *ioc = iocg->ioc;
+ size_t pos = 0;
+
+ if (!ioc->enabled)
+ return 0;
+
+ if (iocg->level == 0) {
+ unsigned vp10k = DIV64_U64_ROUND_CLOSEST(
+ ioc->vtime_base_rate * 10000,
+ VTIME_PER_USEC);
+ pos += scnprintf(buf + pos, size - pos, " cost.vrate=%u.%02u",
+ vp10k / 100, vp10k % 100);
+ }
+
+ pos += scnprintf(buf + pos, size - pos, " cost.usage=%llu",
+ iocg->last_stat.usage_us);
+
+ if (blkcg_debug_stats)
+ pos += scnprintf(buf + pos, size - pos,
+ " cost.wait=%llu cost.indebt=%llu cost.indelay=%llu",
+ iocg->last_stat.wait_us,
+ iocg->last_stat.indebt_us,
+ iocg->last_stat.indelay_us);
+
+ return pos;
+}
+
+static u64 ioc_weight_prfill(struct seq_file *sf, struct blkg_policy_data *pd,
+ int off)
+{
+ const char *dname = blkg_dev_name(pd->blkg);
+ struct ioc_gq *iocg = pd_to_iocg(pd);
+
+ if (dname && iocg->cfg_weight)
+ seq_printf(sf, "%s %u\n", dname, iocg->cfg_weight / WEIGHT_ONE);
+ return 0;
+}
+
+
+static int ioc_weight_show(struct seq_file *sf, void *v)
+{
+ struct blkcg *blkcg = css_to_blkcg(seq_css(sf));
+ struct ioc_cgrp *iocc = blkcg_to_iocc(blkcg);
+
+ seq_printf(sf, "default %u\n", iocc->dfl_weight / WEIGHT_ONE);
+ blkcg_print_blkgs(sf, blkcg, ioc_weight_prfill,
+ &blkcg_policy_iocost, seq_cft(sf)->private, false);
+ return 0;
+}
+
+static ssize_t ioc_weight_write(struct kernfs_open_file *of, char *buf,
+ size_t nbytes, loff_t off)
+{
+ struct blkcg *blkcg = css_to_blkcg(of_css(of));
+ struct ioc_cgrp *iocc = blkcg_to_iocc(blkcg);
+ struct blkg_conf_ctx ctx;
+ struct ioc_now now;
+ struct ioc_gq *iocg;
+ u32 v;
+ int ret;
+
+ if (!strchr(buf, ':')) {
+ struct blkcg_gq *blkg;
+
+ if (!sscanf(buf, "default %u", &v) && !sscanf(buf, "%u", &v))
+ return -EINVAL;
+
+ if (v < CGROUP_WEIGHT_MIN || v > CGROUP_WEIGHT_MAX)
+ return -EINVAL;
+
+ spin_lock_irq(&blkcg->lock);
+ iocc->dfl_weight = v * WEIGHT_ONE;
+ hlist_for_each_entry(blkg, &blkcg->blkg_list, blkcg_node) {
+ struct ioc_gq *iocg = blkg_to_iocg(blkg);
+
+ if (iocg) {
+ spin_lock(&iocg->ioc->lock);
+ ioc_now(iocg->ioc, &now);
+ weight_updated(iocg, &now);
+ spin_unlock(&iocg->ioc->lock);
+ }
+ }
+ spin_unlock_irq(&blkcg->lock);
+
+ return nbytes;
+ }
+
+ ret = blkg_conf_prep(blkcg, &blkcg_policy_iocost, buf, &ctx);
+ if (ret)
+ return ret;
+
+ iocg = blkg_to_iocg(ctx.blkg);
+
+ if (!strncmp(ctx.body, "default", 7)) {
+ v = 0;
+ } else {
+ if (!sscanf(ctx.body, "%u", &v))
+ goto einval;
+ if (v < CGROUP_WEIGHT_MIN || v > CGROUP_WEIGHT_MAX)
+ goto einval;
+ }
+
+ spin_lock(&iocg->ioc->lock);
+ iocg->cfg_weight = v * WEIGHT_ONE;
+ ioc_now(iocg->ioc, &now);
+ weight_updated(iocg, &now);
+ spin_unlock(&iocg->ioc->lock);
+
+ blkg_conf_finish(&ctx);
+ return nbytes;
+
+einval:
+ blkg_conf_finish(&ctx);
+ return -EINVAL;
+}
+
+static u64 ioc_qos_prfill(struct seq_file *sf, struct blkg_policy_data *pd,
+ int off)
+{
+ const char *dname = blkg_dev_name(pd->blkg);
+ struct ioc *ioc = pd_to_iocg(pd)->ioc;
+
+ if (!dname)
+ return 0;
+
+ seq_printf(sf, "%s enable=%d ctrl=%s rpct=%u.%02u rlat=%u wpct=%u.%02u wlat=%u min=%u.%02u max=%u.%02u\n",
+ dname, ioc->enabled, ioc->user_qos_params ? "user" : "auto",
+ ioc->params.qos[QOS_RPPM] / 10000,
+ ioc->params.qos[QOS_RPPM] % 10000 / 100,
+ ioc->params.qos[QOS_RLAT],
+ ioc->params.qos[QOS_WPPM] / 10000,
+ ioc->params.qos[QOS_WPPM] % 10000 / 100,
+ ioc->params.qos[QOS_WLAT],
+ ioc->params.qos[QOS_MIN] / 10000,
+ ioc->params.qos[QOS_MIN] % 10000 / 100,
+ ioc->params.qos[QOS_MAX] / 10000,
+ ioc->params.qos[QOS_MAX] % 10000 / 100);
+ return 0;
+}
+
+static int ioc_qos_show(struct seq_file *sf, void *v)
+{
+ struct blkcg *blkcg = css_to_blkcg(seq_css(sf));
+
+ blkcg_print_blkgs(sf, blkcg, ioc_qos_prfill,
+ &blkcg_policy_iocost, seq_cft(sf)->private, false);
+ return 0;
+}
+
+static const match_table_t qos_ctrl_tokens = {
+ { QOS_ENABLE, "enable=%u" },
+ { QOS_CTRL, "ctrl=%s" },
+ { NR_QOS_CTRL_PARAMS, NULL },
+};
+
+static const match_table_t qos_tokens = {
+ { QOS_RPPM, "rpct=%s" },
+ { QOS_RLAT, "rlat=%u" },
+ { QOS_WPPM, "wpct=%s" },
+ { QOS_WLAT, "wlat=%u" },
+ { QOS_MIN, "min=%s" },
+ { QOS_MAX, "max=%s" },
+ { NR_QOS_PARAMS, NULL },
+};
+
+static ssize_t ioc_qos_write(struct kernfs_open_file *of, char *input,
+ size_t nbytes, loff_t off)
+{
+ struct gendisk *disk;
+ struct ioc *ioc;
+ u32 qos[NR_QOS_PARAMS];
+ bool enable, user;
+ char *p;
+ int ret;
+
+ disk = blkcg_conf_get_disk(&input);
+ if (IS_ERR(disk))
+ return PTR_ERR(disk);
+
+ ioc = q_to_ioc(disk->queue);
+ if (!ioc) {
+ ret = blk_iocost_init(disk->queue);
+ if (ret)
+ goto err;
+ ioc = q_to_ioc(disk->queue);
+ }
+
+ spin_lock_irq(&ioc->lock);
+ memcpy(qos, ioc->params.qos, sizeof(qos));
+ enable = ioc->enabled;
+ user = ioc->user_qos_params;
+ spin_unlock_irq(&ioc->lock);
+
+ while ((p = strsep(&input, " \t\n"))) {
+ substring_t args[MAX_OPT_ARGS];
+ char buf[32];
+ int tok;
+ s64 v;
+
+ if (!*p)
+ continue;
+
+ switch (match_token(p, qos_ctrl_tokens, args)) {
+ case QOS_ENABLE:
+ match_u64(&args[0], &v);
+ enable = v;
+ continue;
+ case QOS_CTRL:
+ match_strlcpy(buf, &args[0], sizeof(buf));
+ if (!strcmp(buf, "auto"))
+ user = false;
+ else if (!strcmp(buf, "user"))
+ user = true;
+ else
+ goto einval;
+ continue;
+ }
+
+ tok = match_token(p, qos_tokens, args);
+ switch (tok) {
+ case QOS_RPPM:
+ case QOS_WPPM:
+ if (match_strlcpy(buf, &args[0], sizeof(buf)) >=
+ sizeof(buf))
+ goto einval;
+ if (cgroup_parse_float(buf, 2, &v))
+ goto einval;
+ if (v < 0 || v > 10000)
+ goto einval;
+ qos[tok] = v * 100;
+ break;
+ case QOS_RLAT:
+ case QOS_WLAT:
+ if (match_u64(&args[0], &v))
+ goto einval;
+ qos[tok] = v;
+ break;
+ case QOS_MIN:
+ case QOS_MAX:
+ if (match_strlcpy(buf, &args[0], sizeof(buf)) >=
+ sizeof(buf))
+ goto einval;
+ if (cgroup_parse_float(buf, 2, &v))
+ goto einval;
+ if (v < 0)
+ goto einval;
+ qos[tok] = clamp_t(s64, v * 100,
+ VRATE_MIN_PPM, VRATE_MAX_PPM);
+ break;
+ default:
+ goto einval;
+ }
+ user = true;
+ }
+
+ if (qos[QOS_MIN] > qos[QOS_MAX])
+ goto einval;
+
+ spin_lock_irq(&ioc->lock);
+
+ if (enable) {
+ blk_stat_enable_accounting(ioc->rqos.q);
+ blk_queue_flag_set(QUEUE_FLAG_RQ_ALLOC_TIME, ioc->rqos.q);
+ ioc->enabled = true;
+ } else {
+ blk_queue_flag_clear(QUEUE_FLAG_RQ_ALLOC_TIME, ioc->rqos.q);
+ ioc->enabled = false;
+ }
+
+ if (user) {
+ memcpy(ioc->params.qos, qos, sizeof(qos));
+ ioc->user_qos_params = true;
+ } else {
+ ioc->user_qos_params = false;
+ }
+
+ ioc_refresh_params(ioc, true);
+ spin_unlock_irq(&ioc->lock);
+
+ put_disk_and_module(disk);
+ return nbytes;
+einval:
+ ret = -EINVAL;
+err:
+ put_disk_and_module(disk);
+ return ret;
+}
+
+static u64 ioc_cost_model_prfill(struct seq_file *sf,
+ struct blkg_policy_data *pd, int off)
+{
+ const char *dname = blkg_dev_name(pd->blkg);
+ struct ioc *ioc = pd_to_iocg(pd)->ioc;
+ u64 *u = ioc->params.i_lcoefs;
+
+ if (!dname)
+ return 0;
+
+ seq_printf(sf, "%s ctrl=%s model=linear "
+ "rbps=%llu rseqiops=%llu rrandiops=%llu "
+ "wbps=%llu wseqiops=%llu wrandiops=%llu\n",
+ dname, ioc->user_cost_model ? "user" : "auto",
+ u[I_LCOEF_RBPS], u[I_LCOEF_RSEQIOPS], u[I_LCOEF_RRANDIOPS],
+ u[I_LCOEF_WBPS], u[I_LCOEF_WSEQIOPS], u[I_LCOEF_WRANDIOPS]);
+ return 0;
+}
+
+static int ioc_cost_model_show(struct seq_file *sf, void *v)
+{
+ struct blkcg *blkcg = css_to_blkcg(seq_css(sf));
+
+ blkcg_print_blkgs(sf, blkcg, ioc_cost_model_prfill,
+ &blkcg_policy_iocost, seq_cft(sf)->private, false);
+ return 0;
+}
+
+static const match_table_t cost_ctrl_tokens = {
+ { COST_CTRL, "ctrl=%s" },
+ { COST_MODEL, "model=%s" },
+ { NR_COST_CTRL_PARAMS, NULL },
+};
+
+static const match_table_t i_lcoef_tokens = {
+ { I_LCOEF_RBPS, "rbps=%u" },
+ { I_LCOEF_RSEQIOPS, "rseqiops=%u" },
+ { I_LCOEF_RRANDIOPS, "rrandiops=%u" },
+ { I_LCOEF_WBPS, "wbps=%u" },
+ { I_LCOEF_WSEQIOPS, "wseqiops=%u" },
+ { I_LCOEF_WRANDIOPS, "wrandiops=%u" },
+ { NR_I_LCOEFS, NULL },
+};
+
+static ssize_t ioc_cost_model_write(struct kernfs_open_file *of, char *input,
+ size_t nbytes, loff_t off)
+{
+ struct gendisk *disk;
+ struct ioc *ioc;
+ u64 u[NR_I_LCOEFS];
+ bool user;
+ char *p;
+ int ret;
+
+ disk = blkcg_conf_get_disk(&input);
+ if (IS_ERR(disk))
+ return PTR_ERR(disk);
+
+ ioc = q_to_ioc(disk->queue);
+ if (!ioc) {
+ ret = blk_iocost_init(disk->queue);
+ if (ret)
+ goto err;
+ ioc = q_to_ioc(disk->queue);
+ }
+
+ spin_lock_irq(&ioc->lock);
+ memcpy(u, ioc->params.i_lcoefs, sizeof(u));
+ user = ioc->user_cost_model;
+ spin_unlock_irq(&ioc->lock);
+
+ while ((p = strsep(&input, " \t\n"))) {
+ substring_t args[MAX_OPT_ARGS];
+ char buf[32];
+ int tok;
+ u64 v;
+
+ if (!*p)
+ continue;
+
+ switch (match_token(p, cost_ctrl_tokens, args)) {
+ case COST_CTRL:
+ match_strlcpy(buf, &args[0], sizeof(buf));
+ if (!strcmp(buf, "auto"))
+ user = false;
+ else if (!strcmp(buf, "user"))
+ user = true;
+ else
+ goto einval;
+ continue;
+ case COST_MODEL:
+ match_strlcpy(buf, &args[0], sizeof(buf));
+ if (strcmp(buf, "linear"))
+ goto einval;
+ continue;
+ }
+
+ tok = match_token(p, i_lcoef_tokens, args);
+ if (tok == NR_I_LCOEFS)
+ goto einval;
+ if (match_u64(&args[0], &v))
+ goto einval;
+ u[tok] = v;
+ user = true;
+ }
+
+ spin_lock_irq(&ioc->lock);
+ if (user) {
+ memcpy(ioc->params.i_lcoefs, u, sizeof(u));
+ ioc->user_cost_model = true;
+ } else {
+ ioc->user_cost_model = false;
+ }
+ ioc_refresh_params(ioc, true);
+ spin_unlock_irq(&ioc->lock);
+
+ put_disk_and_module(disk);
+ return nbytes;
+
+einval:
+ ret = -EINVAL;
+err:
+ put_disk_and_module(disk);
+ return ret;
+}
+
+static struct cftype ioc_files[] = {
+ {
+ .name = "weight",
+ .flags = CFTYPE_NOT_ON_ROOT,
+ .seq_show = ioc_weight_show,
+ .write = ioc_weight_write,
+ },
+ {
+ .name = "cost.qos",
+ .flags = CFTYPE_ONLY_ON_ROOT,
+ .seq_show = ioc_qos_show,
+ .write = ioc_qos_write,
+ },
+ {
+ .name = "cost.model",
+ .flags = CFTYPE_ONLY_ON_ROOT,
+ .seq_show = ioc_cost_model_show,
+ .write = ioc_cost_model_write,
+ },
+ {}
+};
+
+static struct blkcg_policy blkcg_policy_iocost = {
+ .dfl_cftypes = ioc_files,
+ .cpd_alloc_fn = ioc_cpd_alloc,
+ .cpd_free_fn = ioc_cpd_free,
+ .pd_alloc_fn = ioc_pd_alloc,
+ .pd_init_fn = ioc_pd_init,
+ .pd_free_fn = ioc_pd_free,
+ .pd_stat_fn = ioc_pd_stat,
+};
+
+static int __init ioc_init(void)
+{
+ return blkcg_policy_register(&blkcg_policy_iocost);
+}
+
+static void __exit ioc_exit(void)
+{
+ blkcg_policy_unregister(&blkcg_policy_iocost);
+}
+
+module_init(ioc_init);
+module_exit(ioc_exit);